It's really a combination of a good concealable firearm and a proper holster. The MTAC is an "Inside The Waistband" holster. A good holster, with proper clothes, will hide more than you might imagine. Then again, it's gonna be far easier to conceal a baby Glock than it is a Sig P226 or Beretta 92FS.
An IWB holster will conceal much easier than an OWB holster. To be comfortable, however, a small gun is important. On that note, its the grip of the firearm that prints against your clothing. Barrel length doesn't really matter. A single stack pistol will also conceal easier than a double stack, as the double stack grip is obviously thicker. I can conceal my Glock 26 just fine, although my new LW Commander prints a tad less, as its a single stack, even though its a bit bigger.
One more thing to remember is that you will ALWAYS be self conscious to the fact that you're carrying. Every time you move you're gonna wonder if its showing. I do it as well. I'll say though, that most people aren't looking for it, and most will never be able to tell.
Im sure Ive just confused the heck outta ya, and Im sorry! Please keep asking questions, and I'll try to answer what I can!
With you being in a hot environment, I'd say that its more important that you pick an easily concealable firearm. With that in mind, it's gotta be 100% reliable, so no Saturday night specials!
:cheers: