Question: The mental armor 1 provided by the Conviction stunt Tower of faith would reduce spellcasting stress wouldn't it? and we know from the books that one can have faith in magic, so as long as you did the equivalent of praying (probably a quick meditation or an extended drawing up of power) you could cast the easy stuff basically at will.
Ha, cute! Given that the context of the passage says, "Strongly held beliefs enable you to protect your mind from the aggression of others," I'm assuming it wouldn't count for anything self-inflicted. The passage in Evo says the absolute minimum is 1 stress. No exceptions are offered. (Except sponsorship, like I said.)
-L