I think the some raisin flavor and added sweetness would work with a high ABV malty beer. The OG is going to be high enough that I won't need to worry about the fermentables in the raisins. So, maybe this answers the question of when to add....the secondary. How about treating them like a dry hop addition? How much in a 10gal batch, I guess is a matter of personal taste. Does 2 lbs seem like a good place to start?