I'm working on enlarging small primer pocket brass to large flash holes. Alpha Munitions does this on a lot of their small primer pocket rifle brass. Seems to me that it would be the best of both worlds.
There is no way a Hunter slide is moving as fast as a stock 2 or limited slide, so, your experience is the opposite of what would be expected from physics.
Large frame Polymer guns tend to be the easiest and most compatible, even with steel frame uppers. However, the polymer guns are the ones most confused between large and small frame due to the fact almost all wholesalers use small frame pics for large frame guns. Within large frame steel guns, there is a wider variance of tolerances causing more fitment issue. Also steel uppers look cosmetically funny on polymer lowers.
Well, the p322 has a factory 20 round magazine, and they are suppose to have 25 round extended one coming out. I don't have the gun, but did see them magazine at a local Scheels, and it is smaller than most of my handgun magazines in all dimensions.
I mounted the standard sight on my 22lr conversion without trouble: https://store.eaacorp.com/shop/product/303011-standard-fiber-optic-front-sight-303011-179?category=15#attr=
Mecgar is the supplier for more factory mags than any other company I am aware of. Most oem pistol mags I am aware of are actually mecgar. The exceptions are mostly the exteme high volume stuff you'd expect.