Balance on the MWG-90 is not really a problem. If too weak, you can lay it on your arm. And this is clearly not a patrol-all-day sort of magazine.
The problem is that its just sort of a junky magazine. The ones I have seen and used had a soft plastic upper part, that wouldn't feed when hot, and wouldn't drop or insert worth a damn, sorta like the original unlike Glock mags.
Also, its not that reliable. Really hard to load, and only runs 100% when freshly cleaned.
Doesn't mean I didn't sell one in the height of the ban for $70 profit.