I think a 3D’r ought to really look at the underside of the stock, right at the hook, and come up with a wrap around clamp on deal and have two mags capture that space underneath, laying flat against it.
Or, reuse that rear pocket hole and fill it, like the previous mag holders did, but fill it for a place to anchor mag holders to, one at each side.
Lastly, the best idea, I feel, is the way Jefferson State Air rifles did with the wildcat scope rails. They put a slip in channel that captured the ball bearing on the old style mags. The mags just snapped in there. I believe that’s how the Raptor guns are. I’ve talked with JSAR on revisiting that design again(they no longer make it. I was told they only made a few, and not enough folks knew about them to make them a big product mover. I’m one of the lucky ones with one each on both my MK2 cats). To design that, though, would be a machining effort, and not 3D.