lol "mags per fill"
On a marui 1911 with a metal slide, the measurement is actually in "fills per mag"

Good luck getting more than 8 shots off. Take a look at the KJ and socom gear mags, there's a reason they only hold 15 rounds instead of 26

The KJ mags hold 26 and are clones of the TM mags... maybe you meant the WE/Socom Gear and KSC/KWA mags...

My socom gear les baer hold 28bbs in the mag.

The Les Baer is made by KJW and is one of the exceptions, most other Socom Gear pistols are WE.

There is always the Nineball featherweight piston/blow back unit upgrade...

Although it does help, reducing the BBU weight by half doesn't make a very big difference over the stock configuration when you've already doubled the weight of the slide =/

The way I see it, if you run real cap, you'll be okay when it comes to metal upgraded pistols.

I've never had an issue pushing my Glock to 17+1 rounds - nor have I had issues pushing a green gas 1911 to 7+1. Both have metal slides and/or kits installed. There's just not enough gas capacity in a single stack magazine to work with a metal slide on the 1911. If that's a deal killer, the Hi-Capa is a very viable alternative.

I've got a couple SG Punisher 1911's, six mags, and they all work decently well. Depending on temperature and how fast I fire (I tend to double tap), I can get a full mag of BBs out with a fill on most of them.

That isn't much o a feat, considering that the SG (WE rebrands) only hold 15 reds per mag.
Tuned pistols can get easily a full mag per gas charge, my Nova Bodied 1911 gets 40+ shots per mag consistently xP

https://m.youtube.com/watch?v=3rTqkv0AQeI

Shim your gas routers, that can greatly improve your gas efficiency!