Men's Warehouse has been great with me. I have two "Suit Uniforms" from working a Federal contract protection detail where the whole Secret Service look was required. The belt loops were made wide enough for a thick real gun belt and strengthened. The coats were tailored around the gun.
I recently bought a Tux. It was tailored around a P2000SK in an Alessi Bodyguard shoulder holster with two spare P30 mags. This will also work with a S&W 2" Model 12 carried AIWB under the cummerbund with a Model 37 on the ankle if I want a set up where I can take the coat off. I have also used messenger type bags when working protective details that will hold an amazing amount of support gear and do not look out of place in today's office environments.......although I never seem to blend in to those environments and look like "the bodyguard". It is why I prefer to dress like the landscape contractor when I can to better fit in.
Just a Hairy Special Snowflake supply clerk with no field experience, shooting an Asymetric carbine as a Try Hard. Snarky and easily butt hurt. Favorite animal is the Cape Buffalo....likely indicative of a personality disorder.
"If I had a grandpa, he would look like Delbert Belton".
All off the rack, and then tailored. My build generally requires very large sizes in order to get long enough sleeves, and then to be taken in greatly to actually fit me. I'm 6'5" so finding sleeves long enough is a challenge as most can only be let out an inch or less. As for brands, my tux is Calvin Klein, I have a couple Joseph Abboud (now owned by Mens' Wearhouse), these are half-canvassed, and one that I can't recall the brand of, cheap fused.
There will be a three piece Brooks' Brothers full-canvas purchase in the mid-near future. I suit up quarterly, or so. Hence why this is still a dilemma 5 years into my becoming a responsible citizen.
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I may be in a little over my head here on the formal wear talk. Not sure what waist suppressed means. Usually they don't need to do much with the pants other than make them a touch longer. They do take them in a little sometimes in the waist. I don't know what drop is.
They are slim fit suits I recall now that you mention it.
Is this what it feels like when new gun owners come and we are talking about bore axis and length of pull?
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Guys---work with your tailors; they do this stuff all the time for cops, DA's, judges, Federal agents, PI's, citizens with CCW's, etc...
If you want the bottom button undone look, have your tailor fabricate a hidden fastener to keep the jacket from blowing open while still looking stylishly "unbuttoned" or just keep it buttoned.
Facts matter...Feelings Can Lie
No big deal! Drop refers to the number in inches difference between waist and chest So a drop "7" would mean that a 40 jacket would have matching trousers that have a 33" waist. The drop number is a pretty good general indicator of how fitted an off the rack brand is. And this gives me an idea of how fitted you are wearing your suits.
Most Amercian men wear a drop 6 hence the old phrase the American "Sack" suit. Good Brit or continental tailoring usually starts at a 7 unless you have you're thick around the middle.
I would do this for right now: Get a good inside the waistband strong side hip holster in a minimalist configuration like the TT Gunleather Mke's Special and try it with your suiting. The worst case is that it doesn't work and you still have a fine holster. The Mike's Special has some extra cant and might very well do the trick.
If you are going to be taking the jacket off and walking around then it's belly band time and that may very well require some trouser and shirting adjustment.