Since I'm shooting a 29" .340 A/C Superslim out of both my single cam and binary cam bows at 70# with a 125 grain head, I'm going to vote that the 28" .340 with a 100 grain head will be plenty stiff.

EDIT: oops! I missed the 100 grain brass insert... that may shift things. Let us know. I'm interested in using those with a 125 grain head on some A/C/C's when I run out of Superslims.