imho, this thing about stickbows and arrows isn't rocket science. for the most part, most bows and strings and arrows can be made to shoot reasonably well,
for each of us. the common denominator is
us, and the physical and mental differences we each have when shooting bows 'n' arras.
if you can't get a particular bow/string/arrow to shoot reasonably well, change one parameter at a time and give it a fair amount of testing time. if that one change helps, fine. if it makes something worse or offers no change in performance, reverse that change. above all, don't listen too much to the rapping of what does and doesn't work for other archers. make parameter changes that are bracketed both above and below what the "common sense consensus" of the archery community espouses.
personally, i don't have any issues with the beman 500 ics venture/bowhunter shaft in terms of "weak spine". my mohawk t/d is 62" and 55.5# @ 29". i use a beman 500 that's precisely 29.25" from the bohning signature nock's throat depth to the back of the shaft. there's a 100 grain brass insert coupled to a 250 aggregate point weight (125gr point and 125gr steel adapter), 29.3% foc, 585 grains total weight. same 75x105 4" feather 4-fletch. i draw that arrow so that the brass insert is flush with the front of the bow's shelf and touches my bow hand (my version of a draw check). the arrows fly fast and true (if i aim and release reasonably well), with no porpoise or fishtail.
i shoot that same arra, but with a 125 grain point weight, 460 grains total weight, 23.25% foc, from a 62", 46# @ 29" 1pc mohawk. same great arra flight.
i've tried beman 400 and 350 spined shafts - all were too stiff from any of my bows, no matter what the foc or total arra weight.
if it works, don't fix it. :D
29" 585gr beman 500 - before and after an encounter with mr. piggy ...