I am asking all you arrow experts out there. I went to our local hunting store to buy some beman mfx in the 340 size. all they had were 400's. the local expert told me he has not seen them in that size. when i told him my specs; 30in lenght, 65lb bow, 100 grain muzzy, shooting a hoyt vectrix he said that i was right on the cusp of 340 and 400 and that 400 would be fine. My question is; is this arrow going to be to light for my setup?

any advice is greatly apprectiated.