Also I noticed Rapport wasn't on your list as an attacking skill. The Chit-Chat trapping allows one to make social attacks with Rapport.

I listed it...but I said it was primarily for maneuvers, based on the description under Chit-Chat:

A character skilled in Rapport is a master of small talk and, through casual, friendly conversation, can get folks to give up information without quite realizing they’ve done it. In a social conflict, you may roll Rapport for maneuvers and “attacks” with this goal in mind.

I figure there's a certain point when Rapport is harder to use...generally when the conversation gets less friendly.  If you're being attacked with Intimidate, you can defend with Rapport...but it's pretty hard to counterattack with Rapport at that point.

My group has had a lot of trouble with Social conflicts, so I'm trying to make a quick reference sheet for them.  Here's what I have so far...any feedback is appreciated.

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Social Combat Quick Reference Sheet

Initiative:  Empathy

Attack/Defense:
Deceit (cannot use for both attack and defense in the same round)
   versus Alertness, Empathy, Investigation, or Rapport (depending on the type of deceit)
Empathy (assessments only)
   versus Deceit or Rapport
Intimidation
   versus Discipline, Presence, or Rapport
Presence (only versus large groups)
   versus Empathy or Rapport
Rapport (primarily for maneuvers)
   versus Deceit or Rapport

Other possible social skills:
Conviction - sometimes used as a social defense
Contacts - sometimes used as a social attack against reputation
Lore - used versus Lore-based Deceit ("He's not really a wizard...")
Performance - sometimes used for declarations, such as music to soothe the savage beast
Scholarship - used versus Scholarship-based Deceit ("Cars don't explode like that!")
Resources - modifies bribery attempts

But beyond game mechanics, you have here a senior RCV.  You want to play him/her smart.  He/she (hereafter; he for short) doesn't just set traps and make sure he's got an escape route (though he should have both), he seduces, addicts, or buys a host of human shields.  You know, the sort of folks the council would take a VERY dim view of being killed by magic.  He should be making alliances with other supernatural forces so that if the PC's kill him, they will make an enemy of someone even worse - and he should be advertising that alliance, for deterrent effect.  He should be setting up "dead men's switches" on the PC's families so that if he doesn't radio so-and-so by 1600 today, they die.  In short, if he is a major Big Bad, he should be doing everything in his power to make the PC's not want to kill him, because its not worth the cost.
...
Now, since you say there is another big bad setting this guy up, you might use only one or two of these effects.

Sure, you can ratchet up the tension of the final confrontation by throwing more raw force into it.   But you can also ratchet it up by making it relatively easy to kill him, but making the choice of whether to do so really intense.

The key here is what type of game are your players expecting. If they expect to crawl through the RCV's "dungeon" and unload a ton of Fate Points on round 1 and go home, how would they react if you rain on their expectations?

I think they'll be fine with it - they will realize that a quick, easy kill of the Big Bad may be an ego boost, but it won't make for a fun campaign.

Depending on the type of game you are GMing (and it appears quite high powered), perhaps you should ask yourself if the RCV should not be outclassed, even though he is your big bad with every ploy that he might try to stop the PCs either being stymied or countered.

It's about as high-powered as you would expect from a beginning Submerged game.  It's not anything like the games where people are starting at 15+ refresh, but each PC is as tough as "Storm Front" Harry.  Whenever Harry is teaming up with people like Thomas, Michael, and Murphy, he can face off with some seriously major-league threats...and I expect to carry on that tradition in my game.

I expect the Big Bad to be defeated...but it will be a close thing, and the battle will be decided by player ingenuity and a few outside influences hedging their bets.  Despite everything working against him, the guy is a Red Court noble with a lot of RCV's backing him up.

Okay, so I'm running the final to our campaign's second Dresden Files adventure.  The heroes have figured out that the big bad (a Red Court noble) is in hiding in an old mansion, and they plan to go after him.  So, barring surprises on their part, the characters will end up facing the RCV on his home turf, after having plenty of time to plan and prepare.  They're also banked several Fate points during the adventure, and I'm fully expecting them to tag a ton of aspects and turn the big bad into dust in Round 1.  Now, I'm pretty new to FATE, so I may have missed something.  The players have narrative control and die modifiers in the form of Fate Points and Aspects.  What does the gamemaster have, aside from GM fiat and using compels?  How does a bad guy utilize their own aspects in a conflict? 

I want to have a memorable conflict that will shape the rest of the campaign, not a one-sided conflict (on either side).  Once they manage to get into the presence of the big bad, I don't want to have the PCs kill or severely wound the big bad in the first round.  It wouldn't be hard for the combat-capable characters to tag 3 of their own aspects (without even touching scene aspects or maneuvers imposed by other members of the group) to get +6 to their first attack roll.  One even has "Better Dead than Red (Court)", so extended social conflicts aren't an option.

Also, what scene aspects would you give for an old mansion that has been the hidden lair of a Red Court noble for the better part of a century?

The cheat sheet is pretty cool, and I plan to use it (though I may retype it to clean up the formatting).

So...how many of those don't involve Sponsored Magic. Because Sponsored Magic explicitly offers a way around the limit (gaining Sponsor Debt)...and is pretty much involved in every big fight from Dead Beat onward.

So, let's start with Summer Knight (it's fresh in my mind), with the big battle in the sky.  I'm using the paperback, in case it matters for page references.  Starting in Chapter 31, and extending into Chapter 32:
* Pg 342 - Curtain of blazing scarlet energy (to stop bees)
* Pg 342 - Lance of crimson-white energy (used against a giant bee)
* Pg 345 - Smiting the ground to emit a rumbling thunder (to frighten the faerie mounts)
* Pg 346 - Horizontal shield (against charging horses)
* Pg 348 - Bolt of lightning (against Lloyd Slate)
* Pg 349 - Lash of fire (at Talos)
At least three of those spells (shield versus the bees, shield against the horses, and the bolt of lightning) were pushed beyond Harry's normal limits.  The shields covered large areas, and the bolt of lightning dropped Slate and threw everyone else to the ground...well, except Talos.

A better example is Dead Beat.  Both Luccio and Morgan unleash a pair of spells in the first few seconds that Harry sees them, and the combat continues with the following - "More of them materialized out of the rain and the night, but Luccio and the Wardens kept moving steadily forward, burning and crushing and slicing and dicing their way across the street, furiously determined to get the children clear."

I find it very, very hard to believe that Luccio and Morgan only cast a total of four spells each in that scene, when they were halfway to that limit in the first few seconds that Harry sees them (and they were fighting well before Harry arrived).  Harry also uses several spells in that fight, and doesn't call on his sponsored magic (Hellfire) until the final confrontation with Cowl (pg 382).

Those are the two books I have at hand.  Need more examples?

and really it fits pretty well. Harry rarely evocates more than 3-4 times in a fight so that combined with his enchanted items seems pretty fitting

Actually, there are several fights in the books where Harry casts more than 3-4 times.  Some handwave it by saying the spells you cast are just the ones that matter, and there are other spells thrown that are just flavor.

I'd like to see a few more spells thrown, so the house rule I'm looking at is that you can drop the result of the Discipline roll by three to negate the initial point of stress.  This allows a very skilled caster to cast less powerful spells without stress.