Prokop,
It's been a few years, but as I recall the standard kneeling position was to shoot over the leg/knee that was upright, foot flat on the ground, and the other leg extended straight behind you with the calf parallel to the ground. That would leave your rear leg toe on the ground with your foot sticking up Most guys put a padded roll beneath that ankle to stabilize that leg.
I used to take a position like what you describe as I couldn't put any pressure on my knee caps without really severe pain - some sort of bone development problem which I forget the name of. That's why it sounded familiar to me.
I would think for absolute consistent accuracy, the prone position is hard to beat, but probably the least feasible in most field situations.
We shot .22 cal indoors at 50'. Sometimes in summer we would have outdoor matches at 100 yds. That is not easy with a .22 on a breezy day. You had to put a little flag on a wire out in front of you and always try to get your shot off when the flag is in the same postion.
It was good fun and not expensive once you had the target rifle. The sights were iron, peep hole at the rear and ring-on-post in front. We did learn some good shooting skills.
Enjoy your shooting with anything but a scope now, before you need bi-focals
Dave.