use hollow braid nylon poly rope.. I believe 1/4" for that shaft. cut it to length, where the insert will bump it, melt one end closed, insert a piece of wire down the center, and push it in, then yank the wire out should be almost right at the weight desired.. I cannot remember exactly the diamater rope needed so ya might get a couple sizes..I have never found this to affect arrow spine in bare shaft testing (seems like it would) and really quiets the arrow almost to woody level...nock is about 5 gr , 15 for 3 -5" feathers and about 25-30 for the insert