I have 2 of the same frames, one with a 4 1/2 grip and the other 4 3/8 with a full size heat shrink sleeve. When I measure both grips they are exactly 4 1/2, however, the butt cap on the 4 1/2 (without the heat shrink sleeve) is bigger. Is this because a 4 3/8 butt cap, plus a full size shrink sleeve, will be smaller than a 4 1/2 butt cap?