Justin,
First, welcome to what I think is the best gun forum on the net.
I can carry a 1911 comfortably in an IWB because the 1911 is less than an inch wide, at least the part that goes inside the waistband. The USP is wider full size gun and hence takes up a little more room in the pants so you may find you'll have to have a size or so larger waistline pants to make room for the USP.
I'm beginning to sound like a commercial for Fist, but their holsters are top quality, duarable, and most important look good. :biggrin: I recommend a Fist, Inc. #19 IWB holster in Kydex. Fist IWB holsters are made and look just like leather holsters except the Kydex they use in their IWB holsters is super thin, 0.040 inches - that's right, way thinner than a 1/16 of an inch! So they take up a minimal amount of room inside the waistband. If you have a caliper, measure the thickness of your Blade-tech IWB; mine's about .105" thick which is over 2.5 times thicker than the Fist. It makes a difference.
Further, the belt loops that secure the holster to the belt are located off the holster body at the sides, which makes the thickness of the holster even less and the wider spacing adds significant stability against movement. Belt loops located on the body of the holster make the holster thicker.
I have several Fist IWB made their super thin Kydex and have mashed them flat in rool-over shooting drills. The Kydex comes right back to shape.