Michael Jaworski wrote:
if you want to use the K21 as a primary trainer you need to faff around with
installing weights on the tail before every flight where you intend to
spin the glider, then faff around removing them again afterwards.

Actually, I love this. It forces the student to contemplate on the
desired CofG, then weigh the pilots, calculate the needed amount of lead
and finally go up and trust in his calculation. (Which, of course, the
instructor has discreetly double-checked.)

Mounting and unmounting the lead is a matter of seconds and a complete
non-issue. Actually, I think aerobatics is the only application in which
the ASK21 beats the DG1000 because the latter is way too slippery.