Bingo. Jimenez inherited that stoopid design from Bryco/Jennings, and why they never fixed it is beyond me.
Back when I owned Jennings/Jimenez Nines, (I had six of 'em) one of the things I did was to get Bryco Model 59 mag bodies and modify them for my Nine. The Model 59 mag was a heel release, and had no hole at all. You also have to modify the mag body at the top to accommodate the last round hold open function. Then you put the guts from your Jimenez magazine into your modified Model 59 mag, and presto
you've solved the issue. It's not that difficult, just take patience and careful cutting with a Dremel. Measure, take a little away, double-check, and repeat.
Modded Model 59 on the left, factory Jennings/Jimenez Nine on the right:
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