I guess you've already checked and made sure your brace height is right. Are you keeping the inside bend of your elbow perpendicular to the ground? If it's pointed at the sky, it can bring the meaty part of your forearm into the string.

We might could get together on that Friday afternoon. Have to be kinda early though, say 1 or 2 o'clock, 'cuz I gotta go watch my boy do his band thing at halftime of the football game. He's got a marching competition on that Saturday - every Saturday of the month, actually - so my Saturdays are pretty shot in October.[&:]