If the T shirt's too tight, it bulges a little, so I like to wear an over garment with my P90 which, in South Texas, relegates it to cooler months. But, the gun is lighter than a 1911, about like a lightweight commander, and carries well in my Milt Sparks Summer Special. I found no difference in concealment with my old P95, wound up trading that one off after I got a P85 from a friend for cheap, a deal I couldn't refuse. Yeah, the P95 was a little lighter and a little shorter, but it still had that bulge.
Ruger has always had a thing for over beefin' their firearms. The good side is they never wear out and can take a pounding, the bad side being CCW. With the right holster, the P90 is at least light for its size, being about the same weight as a 3" K frame .357 revolver. So long as the shirt is baggy enough, I can carry it. What irks ya though is it's a single stack and could be a lot slimmer.
What I really want is a P90 in the original intended cartridge, 10mm. That was the intent of the design and probably why it's so danged beefy. No, 10 ain't popular and turned out to not be the wave of the future, but it's a good caliber and the Ruger is so danged accurate. It'd be one of the more portable, concealable 10s if they'd do it, too. That EEA Witness is a big gun. The G29 ain't bad, but I don't care for striker fired guns. I hope that striker gun Ruger rumor is false, frankly, or if it's true they don't put a doohicky trigger on it and call it "safe".
That wouldn't be like Ruger, though. They tend to go overboard on the safety thing, too. The P345 is evidence of that.
For true concealment, I've turned to and been quite happy with Kel Tec. I would love to have a Ruger as concealable as my P11, but it just ain't gonna happen. I have several single action Ruger revolvers, love blackhawks, and two P guns. The two P guns, the Kel Tec, and a .380 are my only autoloaders. I'm more of a revolver guy, anyway, but my P90 is so good, it's one of my favorite all around guns hands down. That thing is so accurate and reliable, I'll forgive a little bulge under the T shirt.
It's built like a friggin' tank, too. I know the P97 and the P345 are a little lighter and perhaps flatter, but the P90, in my mind, is the jewel of Ruger's P series, the best of the best. If it's a few ounces heavier than the P97 or a few tenths of an inch wider through the slide than the P345, I'll deal with it.
I also LOVE Hogue's finger groove grip for P guns, something you can't put on a plastic frame and the Handall ain't quite the same.