Minimum acceptable self-launch climb rate

"You can simulate an engine failure during a launch at a safe altitude. I've done
at 2000'-3000':
- set your flight recorder to 1 second intervals, to get the best flight trace data
- at altitude, configure the glider for takeoff: gear down, flaps normally used
- line up on a long, straight road or similar
- establish a steady, full power climb at your normal climb speed
- climb for 200' or so, then set throttle to idle, and do a 180 degree turn,
lining up on the that road
- repeat the test, but this time, turn the ignition off, then turn as before"

You cannot do that last bit in an Arcus M - when you turn the engine off it commences the prop lowering process. In the ASH 26 I had before I did try this sort of stuff and would have been confident of a turn back from 200 foot. I think it would also be fine in the Arcus. However from my club's small grass field I am vulnerable to a potentially damaging off field arrival from about 50 foot to about 200 foot.

The only relevant power failure I have had was in the Arcus just after lift off, at 5 foot or less off the ground. There was a drive belt failure, and the glider plonked down rather heavily on the ground - instead of the lift component of the engine power I now had no power and a high drag prop mast.. Happily no damage done other than by the flailing drive belt(s). Since then I have tried to stay just above the ground until achieving say 55 knots.

In the Arcus while best climb rate is supposed to be about 52 knots, you can climb quite a lot faster without over-revving and without much sacrifice of climb rate - and there is a rev limiter which you could only hit in level flight, probably about 90 knots.