Carbonwood 55/70-4000 have a .350 spine and your bow is not cut to center,those arrows are too stiff.I don't think you will be able to tune no matter how much weight you add.I picked up some used Carbon Express 45/60-.400 spine that were already cut 1" past my draw.And they were showing alittle stiff,so I thought I could add more weight to weaken the spine.They got worse the more weight I added,they were in effect bouncing off the riser instead of flexing around it.I did tune a .400 spine to the same bow but they ended up about 2" longer then the other .400 spine arrows.This was on a longbow not cut to center.Carbons are a dfferent animal in tuning then wood or aluminum.I never just cut a carbon without first shooting it full length and trim and tune from there.I find that on longbows not cut to center,a carbon that is longer will tune better and easier.If you have a bow cut to or past center they will tune easier.Carbons recover so much faster from the paradox then other arrow materials.your bow may tune better with a .500 spine carbon or a .400 spine depending on length of the arrow.This has been my experiences with carbons and longbows not cut to center.