I have seen people carry up to a Glock 19 in an ankle holster, I have a Safariland ankle holster that I think was the best ever developed, it is a neoprene sock if you will, that you pull over your shin and zip up, it is made for a J frame S&W, it is extremely secure and does not print, you can run at full speed and have no worry of it going up, down or sideways, or coming out, down side is my legs got bigger and I can no longer wear it, and it is hot as hell, the neoprene makes you sweat. I need to take pics as this is something few have seen, maybe Michael, but few others.
If you decide to use one, get an ankle weight on the leg your going to carry it on, and wear it for a couple of weeks, as your leg needs to get used to the imbalance.