To my knowledge, all current MecGar production is 15 round.
As regards the Browning/Saive HiPo design being perfection incarnate, come down from the mountaintop...that internal extractor has been gone for some long time now.
The Savage pistols were one of the few preceding designs offering a double stack handgun magazine; the HiPo's name came from its (then) amazing 13 round capacity. Everybody else had single stacks.
Let's back up and take a deep breath. Magazine design has made great leaps since 1935; again, witness the 365 9mm pocket pistol with a 10 round capacity.
Doubt this? Take any modern mag, fill it to capacity, there's just enough slack to lock in against a closed slide. Older mag designs have more slack.
Adding two rounds shouldn't put the design to the edge of failure, done by an outfit like MecGar.
Are magazines consumable parts? Absolutely. You'll want spares, and keep an eye on individual mag's performance. I number all of mine, and keep track of any troublemakers. Two of my 365 mags had duff springs early on; I fitted replacements.
So keep an eye on your mags, especially high round count examples, clean, replace springs as needed. Treat mag maintenance just like replacing springs elsewhere in a pistol.
Moon