OK. I ran a quick trial.
Setup: cargo pants, a little baggy, Aker B21 belt, polo-style shirt, also a little baggy, and a full-sized pistol. (Even though you mentioned khakis in the OP, I went with my cargo pants. I have worn my Theis holster with khakis and a sportcoat on many occasions, and the cargos will work fine for this test.)
The Theis is very tuckable. Even having done it only once, it was easy to get everything in place. It took only a few seconds longer than it does to wear it IWB with the shirt tucked behind it. It felt just like it does when I wear a jacket over it, so it should be comfortable all day for me. Once I got the shirt tucked, I tugged on it just a little to loosen it up, and that solved the printing problem.
Looking in the mirror, I felt like the whole setup vanished like it should have. Of course, the clips (black) were visible over my belt (brown), but Tommy also sells clips that go behind the belt, so that's a problem that can be solved. Like any concealment setup, those who know what they're looking for might spot it, but I don't feel like the general public will see it.
A gunfight is not the time to learn new skills.
If you ever have a real need for more than a couple of magazines, your problem is not a shortage of magazines. It's a shortage of people on your side of the argument. -- Art Eatman