Well WE992, I never knew that and am happy to be corrected. I must admit that it certainly doesn't sound like a good idea (and I've flown gliders off the winch at a lot of different airfields, so am very familiar with winch launching) but quite clearly Bruggen, Gutersloh & Laarbruch made it work.
Any ideas why Marham couldn't? If I may make a guess - different eras?
So Enig, what's the scoop?