Aside from your bare shafts hitting where your fletched shafts hit, how do they fly? Straight, nock left, nock high? I agree with moving the nock point up, but suspect that isn't the whole answer. From my own experience, 300 grains up front would make for too weak of a spine under the conditions you specify. FWIW, my nock points for 3 under vary from 5/8" above square to 7/8" above square, with the arrow being nocked under the string nock.