OK - as requested, here is my review after some experience with the shirt.
While I haven't had a lot of opportunity to wear it for extended periods of time, so far I have been satisfied. I've had no event to dress up and walk around all day with it, but I've worn it around the house for the good part of a day and out and about for shorter trips.
I tried wearing it for a while with 2 guns at once, and this seemed to put a good balance on it. I imagine putting a spare mag or two opposite your gun would give the same effect (as it does with my OWB belt holster). I wore it for a bit with my Hi-Power under my left arm (strong hand cross-draw) and my PA-63 under my right arm and it was quite comfortable and stayed in place.
I wore it out to do some laundry for a few hours on two separate occasions with only my Hi-Power under my left arm. This is usually a situation where I'm at somewhat at a loss for a good carry position, as I'm generally dressed in shorts and a t-shirt. In the past, I've put my PA-63 in a Galco 100 IWB holster inside the elastic band of my shorts and thrown a vest over that for concealment. This time around, I opted for the holster shirt, the same shorts, and my normal work shirt attire as cover (the red one that I wear more seldom and was still clean). I certainly knew the Hi-Power was there, but it stayed put and was well concealed. It is certainly preferable to the IWB setup I had used previously.
The Hi-Power is an all-steel gun, and has quite a bit of weight to it when loaded down with 15+1 rounds. It has bigger difference in slide width and grip width, so it opens up more of the pocket towards the top and moves a little bit in that open space. With such a weapon, I would probably not go mountain biking with it... not that I'm worried about it coming loose - it seems to be pretty secure. I just wouldn't want the gun bumping me in the side from the slight lateral movement that occurs because of the difference between slide/frame and grip width. The PA-63 (a lighter aluminum-framed copy of the Walther PPK - same size and roughly the same weight as a Bersa Thunder .380) rides much steadier, and I imagine even a 1911 would do well with this shirt due to its thinner grip making the pocket a more uniform thickness. Unfortunately, I don't have a 1911 to test with (yet), but I will give a report when I do get one. I've read of people carrying service-model Glocks and XDs in this shirt with no problem.
As far as sizing goes, the chart on the 5.11 site seems pretty accurate. I have a 52" chest, and purchased the 2XL shirt. It fits me nicely. The shirt is a spandex material and is quite stretchy. I imagine if you wanted a snug fit, you could probably order a size down and have no issues. I may try this and see if it eliminates the small amount of movement I get with the Hi-Power at a later date.
Overall, I have been very satisfied, and believe that the purchase was $40 well spent. Once I get some dress-up experience with it, I'll give a review of my experiences then. Perhaps I'll dress up for church this Sunday.
