I picked up my new 9mm Tac Ultra FS HC model 51679, this is the double stack with full rail and mag well, on Thursday. I'm very pleased with the pistol, it has the new ramped barrel, slide to frame fit is excellent, as is the barrel lock up. The trigger was much better than I was expecting based on others reviews, some creep no over travel and fairly light, around 4#s. .
For mags I tried using Mecgar Para mags with the Dawson 140mm base plates and Dawson modified Arredondo inserts. These dd not allow me to get more than 16 rounds in the magazine. I also tried the same set up with Arredondo springs and followers, that allowed me to get 20 rounds in the magazine, however they do not lock the slide back after the last round like the factory mag. I'd really like the slide to lock back when empty and still get 20 rounds in a 140mm magazine. I may order an STI mag to see if that will do the trick, unless someone else has a better suggestion?
I made a few minor modifications before firing, the extractor had to much tennson on it so I adjusted that as well as radiused the extractor hook slightly. The breech face and feed ramp were both fairly rough so I polished them both lightly. Then I took it out and shot it today. Accuracy was outstanding, as good as any other 1911 I have owned, including SIg, S&W, Kimbers and Springfields. It was 100% reliable for the 100 rounds of WWB I put through it. However ejection was a bit week with most brass landing within 2-4' of me. It may well be over sprung, or just need some more rounds for break in. I'll likely order a few diferent springs to try out and possibly a new extractor, just because I like having spares.
The factory magazine that came with my gun had a plastic base pad, not metal as others have posted. Perhaps that is the base pad advanced tactical is selling? It looks like the new ones at least are plastic.