RE: a little help
Most of the modern bows coming out are warrantied down to 5 grains of arrow weight per pound of draw weight (360 grain arrow @ 72# draw). To me that sounds ludicrously light (and you wonder why you hear so much about limb issues?) Used to be that the benchmark minimum was 6 grains per pound. You could put a 125 grain head on those .340 shafts and probably still be fine with the spine and you'd gain some FOC, you'd also be above 5 gpp (although just barely).