For me I never just cut a carbon first without shooting them.I start full length with the point weight I plan on shooting and tune and trim the length until I get the dynamic spine I'm looking for.You can tune and trim carbons without gluing the inserts in.What I like to do for my carbon arrow tuning is to use saran wrap.You can use alittle saran wrap and push the insert in with the wrap.It will hold the insert in snug enough for shooting.Then you can pull it out and trim and shoot it again.You will need a softer target like a bag target,so it doesn't grab too tight to pull the insert back out.I shoot through a shallow cardboard box,like 2"deep.The box will hold the arrows angle and the bag target won't grab too tight on arrow removal.I get my arrow tuning done without using any heat and without gluing.Then when I'm satisfied I'll prep the shafts and inserts for epoxing the inserts in.