Re: PSE TAC 15 crossbow - which broadhead are you using?
I still use a single tiny o-ring at the base of every broadhead. This allows up to a quarter of a turn of extra rotation on the broadhead as it tightens. This is enough to insure that the broadhead is correctly aligned and plenty tight enough to maintain its position for many each shot.
The o-rings or tiny rubber-bands are sold at any archery shop that carries broadheads. If you need a link to them let me know and I'll send you one.
Years ago, on aluminum arrows, we would simply heat the shafts and rotate the insert with the broadhead connected to align all broadheads to the same exact position. The inserts were installed using "Hot Ferrule Cement" by Boning or Easton. Today's Carbon Shafts can't be heated the same way without damaging the carbon layer, so other methods were developed to get around the problem and still end up with good alignment.