Ty with your draw and 100gr inserts you should be able to spine tune a 500 shaft on your bows, you will probably need to leave them long though so let your bareshaft tuning tell you what it needs to be. Just put the 100gr insert and 125gt tip in a full length shaft and shoot, holding your bow straight up and down, if it is weak, cut 1/2in off and shoot again, keep trimming off the nock end until the enter the target straight or just slightly weak. If they are stiff you will either have to add more tip weight or go down in spine.
With a good release and form it really is a simple process and tells you exactly what you need to do. Can also fine tune your nock height setting as well, but be sure to have it nock high enough to start to eliminate any shelf contact errors.