Thanks for the questions. The biggest (and heaviest!) semi-auto that I've personally ever carried in an ankle holster was a Star Firestar M40 in 9mm. At first, I carried it in a Uncle Mike's small simple semi-auto ankle holster. It even had a secondary band that went up your leg and then fastened around your let just blow the knee. Even with that, it just didn't feel secure enough, especially when jogging or running, so I tried several others. The one that felt most secure at the time was, if I remember correctly,, a leather ankle holster by DeSantis or Galco. But this was many years ago, and there are many more choices out there today. I also carried a J-Frame size revolver, Smith and Taurus, in an ankle holster. But once again, that was many years ago, so the folks that have carried more recently will be of more help.
There are two points that you don't mention, but which are very important. First, the kinds of pants you wear become a consideration. In order to extract that pistol from that ankle holster with any kind of fluidity or ease of motion, you have to wear pants with fairly loose legs. Straight leg jeans, for example, are just about out of the question. With a little trial and error, you'll find that almost any pants with cuffs will allow easier access than pants without cuffs. The second consideration is leather vs. synthetic material. With that ankle holster down there so near the ground, most folks may not spot it, but don't be surprised when the neighbor's pooch starts sniffing around your leather holster. Once again, it was a long time ago and maybe they have changed the smell of leather ankle holsters, but I had a couple of dogs who decided my leather ankle holster was a real attractive chew-toy and one of them even peed on it! Not good. Let us know what you decide.