I'm intrigued by the logistics of this concealed carry shirt.
Assuming you concealed carry every day, I'll assume you don't wear the same shirt every day, how many shirts do you end up owning to cover daily concealed carry?
What is the lifespan of these shirts when washed regularly.
I only carry when I leave my property, which these days (I'm retired and widowed) is around 2-4 times/week. Call it around 24-30 hours of intermittent wear per month.
I wear a regular cotton T-shirt under it. In summer I rotate the carry shirts about once or twice a month (I have five at present), and in winter I usually just wear the same one the entire season. Undershirts absorb my sweat and the spandex doesn't hold odors like other fabrics.
I've yet to truly wear out one of these shirts. I have worn a hole near the neckband on one of them that I need to darn, but even that shirt is still useable.
The elastic fit begins a gradual loosening around the 6-8th washing. My oldest shirts are hanging pretty loosely now.
Downsides:
Drawing from the velcro pocket is slow. A loose shirt worn tail out seems to work best for me.
Avoid the cheap no-nameo cotton versions -- make sure to get one made of reinforced spandex.
Usually the velcro is sufficient to hold when leaning deeply forward, but I have a habit of automatically bringing my left arm inward a little to trap the gun as I begin bending at the waist. I don't think the maneuver telegraphs anything, and it seems safer to me than risking a wardrobe malf.
There is a distinct upper weight/size limit to suitable handguns. It works well with a 3" J-frame or my Glock 19 with the neutered 10-shot mag, but a Glock 21 of roughly the same size proved too heavy due to the greater weight of .45 ACP ammo -- shirts would stretch and sag on that side. On the other hand, with something like an Airweight or LCR, I've frequently been so unaware of the handgun that I had to run my hand over my shirt to confirm I hadn't forgotten the gun at home.
If I want access, I can't wear my "Will work for ammo" or Sociedad Largo T-shirts on top of it!