On my Spring Check a year and a bit ago, we were using 36 and had a good crosswind from the left; so, I told the checker that on a rope break above 300' I would turn right and land on 03 as the x-wind would set me up nicely.
Up we go and I'm calling out every 100' and pointing out potential landing spots; at my 300' call, the fiend in back pops the release; so, nose down, wait for 55 kt, turn, and start working the spoilers.
Turnbacks from 300' in a glider with 30:1 glide ratio are pretty straightforward. With your average piston single with 10:1 glide ratio, I'd want 900'.
Now there are courageous operators who do practise rope breaks and turnbacks from 200' in Schweitzer 2-33s -- not much margin there, nor would there be in a piston single at 600'. From that height everything has to be done just right.