hockeymom27, I have used soy flour for SOME of the all-purpose flour in most of my recipes (sweet or savory), and it has worked out pretty good so far. For every cup of regular flour, I substitute 1/8 of it with soy flour.
Also, I would substitute some of the sugar for splenda and I would use LOL Light butter for the regular butter in this recipe. The pound cake will only have the "crunchy top" for a few hours after it cools, though, so serve immediately. Lighter cakes get "tacky" on top by day 2! I often remedy this problem by cutting a recipe in half to ensure their are no leftovers. (Of course, in a trifle, a tacky top wouldn't really make a difference..)