I do like the nice even look of the torx. They set down so easily in the micarta of the 4.1, just like Psybull described. I didn't get so lucky on the G10 of the 3.5. I don't know if it's just the rigidity of the material, but I did have to touch the factory-drilled holes with the spotting drill in order to get the torx fasteners to set in where I was satisfied.
Also, a note on the 3.5. The fasteners for the new model 5.1 are three different lengths. If you're going to retrofit an existing 3.5 with these, use the shortest fastener in the hole nearest the blade, and the middle-sized fastener in the other. Both of these require a small amount of material to be ground off the post in order for the screws to tighten up, like Psybull describes with the middle screw and post in the 4.1.
Since the rear post of the existing 3.5 fastener and the shortest post of the 5.1 fasteners are the same length, I tried to use it in the rear hole of the 3.5. I did this thinking I would only have to grind one post shorter instead of grinding a little bit off two posts. What I didn't realize is that the female portion of each of the 5.1 posts are recessed in different depths, so cutting down the middle-length 5.1 fastener and trying to make it fit the front hole of the 3.5 didn't allow the screw to thread down far enough into the post before bottoming out. Should have been easy peasy, I had to go and make it difficult. Just use the short fastener in the front, and the medium fastener in the rear and it goes fine. Hopefully this will keep someone else from doing the same.