You can always take your Heavy Woods and taper 'em down like Howard describes in Hunting the Hard way..... Start 2-3" back of point, then half way point, and finally at around 6" or so from the nock, gives a nice full length taper from 11/32"-5/16" or if your slanging 3/8" they will taper down to 11/32" or there a'bouts. Should decrease spine about 8#, add 150g heads to take out another 5#, so your 80# shafts will shoot out of approx 65# bows close enough "for government work" maybe take away another 5# if your feeling frisky and using F/F, to make spine of course
I also had a few 70-74# shafts but no bows, any longer, in that weight class, soo...... out came the stanley hobby plane, poof 65# full length tapered shafts baby!!!! of course the deer weren't impressed, but beats letting them sit there while I contemplate getting strong again to shoot 75#
and when the girt in your loins are feeling it