Well Roy, you done sent me in a google goose chase, been looking at 550 spine!
Funny thing, they do exist, victory, blackeagle, and some others make them. But i gots too many R’s to be buying more! Most all my arrows are 29”, I draw 27”, so little play. The black ones I shot are 30” and do best, so I’ll stick with them. Those new fancy micro diameter shafts with outserts are nice, come in 550 spine, but price hurt my feelings! Especially with several dozen around here, and most bought for $40 per dozen. I watch clearance sales!