I got all 7 of the new extensions in this week. Shipping was quick and everything came in good order.
There ended up being a few more artifacts than the earlier version but nothing a few minutes, a thumbnail and a lighter couldn't take care of. Just part of the game with 3d printed parts. I'm super picky, to be fair.
My first mag was a complete ****show. I obviously wasn't holding my tongue right and the spring plate kept getting cocked and the spring kept getting bound up. I had to remove the extension multiple times, while trying not to break anything. The spring took some odd bends each time but were easily corrected. I finally got it to go and the rest went easy as pie, the first time. I did adjust my technique with the wrench and found the method that worked best and closely matched the instructions. Without a visual, you could use the wrench incorrectly, in a number of ways.
Once I nailed the wrench technique, they all went on fast, the first time. I did the last 6 in half the time of the first one. One other tip is once you slide the extension back and remove the wrench, if the spring plate doesn't seat on the extension by itself, give the mag a good firm tap on a hard surface and it should pop into place.
The locking piece is interesting and a good solution. They all fit very well, with close tolerances. The screws are of good quality and all but one had very similar resistance, while installing, and locked in flush. One was noticeably looser than the rest, but it still locked in with enough tension that I'm not worried about it. Hole diameter can get tricky with 3d prints, so that's not surprising and the tolerance shift is actually ridiculously small. I think this will be plenty to keep the extensions locked onto the mags.
The included wrenches worked ok but both ball ends rounded easily and made it near impossible to turn the screws, even when not turning from an angle. The short end remained useable throughout, so I expect possibly an uneven heat treat or perhaps undersized machining. Neither side fit the fasteners as tight as I would like but that's super common with generic wrenches and really no fault of the seller.
My one regret is that I was too stupid to realize I was standing right next to a full set of long shank t-handle allen wrenches, the whole time. I wised up on the last mag. That would have made the slowest part much faster.
The new design is pretty cool, well thought out and quite strong. I like it quite a bit, off the gun. In the gun, I'm not sure which version I like better. The new one is more streamlined, likely stronger and will probably work better, ergonomically, than the earlier version. The older version seems to fit the design a bit better, but the new one fits the profile better, if that makes any sense. The only design improvement I can think of would be to remove the side indents, and incorporate some "keltec grip blocks", to match the grip. That's purely cosmetic and subjective.
In the end, the new version holds more ammo, so that's a first place finish, regardless of the cosmetic differences. I would gladly buy again and would highly recommend to anyone looking to hicap their hicap.