There used to be a Grasshopper (or maybe it was an SG 38) in the Bicester hangar when the RAFGSA was still based there. It had an altimeter and ASI fitted (cheat!) but I never actually saw it flown.
Yeh Gods that's going back a bit, it was sold (along with the Fauvel or "Budgie") after Andy Gough died as it was deemed too dangerous for the "modern" winches.
Not sure if it is a myth but someone challenged Andy to give them a free aerotow if they flew the said Primary naked, Andy agreed & promptly towed them to 200 feet on the far side of Bicester town & kept flying a racetrack pattern until the tug's tanks were almost dry (in excess of an hour)
I seem to recall that the flight was re-enacted at Bicesters 40th(?) celebrations afew years ago with a more modestly clothed pilot