While the section on attacks clearly does not include shifts for persistence, the section on prolonging spells on YS259 gives a way to prolong spells that does not include adding shifts of persistence to the initial spell using its base mechanics. It works differently from how you would normally exchange shifts for persistence in a block or maneuver. It does not specify any restrictions on type of spell. How does this interact with attack spells?

I am not sure if this goes against the spirit of an attack or not, in the books a continued flamethrower effect might be cannon depending on how you interpret it through game rules. Balance wise the reduced cost of extending powerful block using this method might offset the ability to continue a powerful attack.

I'm looking for any official information from someone like a game designer, if they are on this board, or something in the text that specifically allows/disallows the prolonging of attack spells. Or perhaps a previous thread that answered this definitively. I have searched but found very little.  Thank you.