I finally got some time to do this review. I got to say I'm not overly impressed with this belt holster. But it does the job and it's quite firm.
The base is bigger (wider) than I thought, here you can see the size compare to a K20D.
This is the plate that you screw to the K20D tripod mount. As you can see there's some scratch already as a result of my first try of mounting the plate to my K20D
It's because the plate top surface is not covered with high friction rubber just like all good tripod plates, it's just shiny smooth slippery plastic. K20D plastic is apparently stronger so it didnt get scratched at all. Still, I need to find way to somehow add friction to this surface. Until then I don't think I'll really use this holster.
You have to align the plate in vertical position so it looks like in the picture below (Note the round end must face toward front of camera). Unfortunately it's not easy because of the low friction of the base which touch K20D body. I managed to tighten it at the first time, but then it's very hard to remove it. So this time when I took these picts I didn't really tighten it.
This is how the K20D with DA 12-24 hanging on the holster. Since I didn't really tighten the plate to K20D, in this picture you can see that the heavy 12-24 is pulled by the gravity and caused the K20D to rotate a bit. If you completely tighten the plate this should not happen.
When my K20D hanging on the holster it's actually quite firm. In fact, I could not take the camera off with one hand like in the advertised pictures, I need another hand to hold the base while I pull the camera. Took a couple seconds the first time but it's getting easier after. Still, I'm not going to win a duel using this holster
I've said that I plan to use the belt holster together with my R-strap. I just realized a flaw in this plan. You see, both the belt holster and R-strap have their own plate but only one of them can be attached to the camera tripod mount
My work around is to attach R-strap to the neckstrap lug instead, with a help of extra ring. Also, it seems natural to use hand grip together with this holster, especially when R-strap isn't used. But hand grip also requires special plate with a lug / hole where you loop the hand grip string / strap, and unlike R-strap plate this belt holster plate can't do that.
This is how the camera hanging with R-strap instead of the holster. It doesn't look very safe honestly. But it's just an extra precaution in case my hand slip. So most of the time the camera will be attached to the belt holster instead. I won't use this setup with my 80-200 lens though (normally without the holster I also don't use R-strap with my 80-200)
So, in conclusion. It works and it's cheap. But it's not fast and a little awkward to pull. And the tightening is worrying (at least for me). Also, it would be nice if it can work together with a hand grip.