I find that carbons when cut shorter then 28" really stiffen up.I would pull the insert and try putting in the 100 gr. insert with your point weight and shoot one before cutting.Alot will depend on how your riser is cut.I bought some used carbons years ago that were 1" past my draw and showing alittle stiff.So I thought I could add more front end weight to weaken the spine.But the more weight I added the worse they got.They were showing even stiffer.They were bouncing off the riser instead of flexing around it.Carbons recover so much faster then other arrow materials.I would try it first before any cutting of the shaft.