I carry my 3913 regularly in a Supertuck, and it works wonderfully. While it's not a full-sized 3rd Gen, I imagine the larger models will work just as well, especially in a lighter alloy-framed model like the 5903.
As for the "combat cut", it is not actually necessary in all cases. I wore it for a year or so without the combat cut, and had no problems with my draw after a little practice. You can still get a full firing grip on the gun with the full backing, it just requires a little more effort to push the backing away from the grip. I later did the "combat cut" myself in about 30 seconds with some shears, and while the draw is slightly easier now, it's not quite as comfortable over long periods of time, especially with rough-textured grips. I actually appreciate that he allows customers the option between giving the holster an edge in comfort, or an edge in ease of presentation, depending on their preference. Different strokes for different folks.
If you're a sweaty guy like me, I recommend the horsehide backing over the cowhide. I've sweated on my horsehide Supertuck through some long Arkansas summer days, with no problems so far.
And at this time, at least, the MTAC is not available for 3rd Gen S&Ws. I have one for my Sig P220R, though, and it works just as well as the Supertuck. The fit and finish is a little bit better than the Crossbreed, but it's also slightly bulkier.