You probably won't gain a whole lot of speed, but will pick up some. When I use B-50 on my longbows, I notice a lot more handshock. Much less with FF.

I dislocated the base joint in my bowhand thumb - right where the bow's grip lays when shooting - playing basketball in college. (Good grief, that was nearly 35 years ago!![:-]) That joint is really sensitive to shock and vibration. Bad, very bad, for an aging longbow shooter. So, that's the main reason I use FF on my longbow.