I have been working with Eric of Yeti Wurks. More like hounding him with requests to make me one more than anything else. Eric has made a name for himself making 3D printed upgrades for the CZ-USA Scorpion Evo 3. His grips are amazing. He has dabbled in making US made base pads and even made a +3 rd extension. I reached out to Eric to see if he could extend it to add 10 rds. He told me he had tried and sent me his prototype. Unfortunately it didn’t quite work and needed some tweaking. One of the biggest issues was getting a magazine spring that would work and feed the 40 rds of 9mm. I had some springs that could work. Here is the second prototype and it works flawlessly. There are a couple issues that are being corrected now and I am waiting on the third version of this +10rd mag extension.
I test ran the mag at a local USPSA match.