I purchased some of the 75 gr Premium broadhead adaptors some time ago from 3Rivers.They were designed as an improvement over some of the existing 75 grain adaptors that had some strength issues.
They had gotten tucked away in my tackle box.I have been trying to tune a set of Gold Tip Trads and it was looking like I needed about a 235 gr point weight for my setup.I had a few 160 grain STOS heads and decided to try those on the 75 gr Premium adaptors.
Evidently,the ferrules on the STOS must be very accurate,as they fit perfectly,and all three arrows that I set up needed no broadhead aligning when I checked them on my spinning jig.I can't remember that ever happening.
One feature of the Premium adaptors that I forgot about,is that the taper is spiral cut,not just grooved.I put the adaptor in a shaft and twisted the adaptor into one of the STOS heads for a trial fit and I could hardly pull it back out.Before any glue!This is a good thing.I really like that feature.
I glued 3 of them up,and re-checked them on the spinning jig and they still spun true and shot right with my field points.
The only thing I would do differently,the next time I use these adaptors,is to not glue my inserts in the shaft beforehand.I was able to get all three broadheads turned to be horizantal,like I wanted,but on one,I had to use pliers to get that last little bit of turn,it was threaded into the ferrule that tight.If my inserts had been loose,it would have been easier to do that.
If you haven't tried these,you may want to give them a look.I plan to order some more in 75 and 100 grs.I wish they also had a 125.That "threaded" taper really locks into the broadhead ferrule.That should make for a really strong bond.