[Gary Brommeland]

Howdy and welcome aboard!
The proper IWB and clothing combination will go a long way toward giving you the maximum possible concealment. The key word here is "possible". You have a thin frame, and the USP is a very large pistol - even in the compact version. I believe that there will be a bit of a "bulge" with whatever holster you select.
A 1911 is MUCH flatter, as would be a small to mid size Glock. If you are really sold on HK products, a P-7 is truly the ultimate carry 9mm. With any of those pistols, a good IWB would most probably work well for you.
However, I am 6'2" and weigh in around 245 lbs, and I cannot wear a USP and achieve what I consider to be an acceptable level of concealment. In short, a good holster can conceal a firearm without making it any bulkier, but as of yet, none of us have figured out a way to shrink your gun for you :smile:
A really oversize "Don Ho" shirt might work with an IWB, but I really think that your USP should be your glovebox/nightstand gun. A smaller firearm would solve the problem more effectively than wearing really oversize clothing.
Please feel free to give me a call if I can help you sort this out (and I won't twist your arm to buy a holster, either). My shop phone is 423.733.1779. Good luck!

 

[Gary Brommeland]

I second the Center of Mass safes, they are great.
However, I've owned Colts, Springfields, Kimbers, Smith and Wessons in 1911s and every single one of them had reliability issues. If I was going for a thinner model, I'd go with the Browning Hi Power.

The HP is a good suggestion. I never trust any 1911 unless it has had some reliability work done to it, and it has had a boatload of rounds thru it.
I've got one left that I have not sold off. It is 100% and it is my "summer" carry gun. Everything else is a Glock.
If 9mm is your caliber, it is really hard to beat a good Glock 19. They are no thicker than a 1911, smaller in length & height and usually totally reliable. They are also very light weight, which adds a great deal to the comfort level.
A Sig 239 would also possibly fill the need, too. The bottom line is that the HK's are so darn thick that they are hard for most folks to conceal properly.