Tim, I use MTG CMJ 124. OAL is 1.160 to 1.163. STI mags .355 in front .360 at rear. Stainless steel floating spacers, Grams 9x19 followers, 13 coil springs in 170 with 3mm base pads, 140 13 coil springs with 7mm base pads. The 170s hold 28 and the 140s I only load 22, the 140 can hold more but are hard on springs.
I had feeding problems with MTG JHP.
STI mags' feed lips are easy to adjust and tune.
I have some old SV mags, which run with no problems. I had problems trying to adjust the feed lips on SV mags, they are like spring steel. The SV mags also had drop free problems and it took about three hours of sanding and fitting on each mag to get them to drop free. If you look inside the frame you will see a ledge, the top side of the SV mags hit on the corners of the ledge. If you bevel the edges where the mags hit they will drop free without working on them. The STI mags are narrower near the top and do not rub against the ledge.