My previous 26E parking brake was a piece of broom handle with a rubber cap on one and a notch cut in the other to fit the back of the spoiler handle. It just wedged in front of the spoiler handle and held the brake on. Handy for short term use.

No hydraulic brake should probably be be left locked on over large temp changes, we'll see what Schleicher say when the Piggott hook/park brake kit arrives for my 26E.