I suggest you contact Aeroclub Phoenix Brüggen e. V., or direct Jan Omsels (German Glider Champion 2013, born there in Elmpt) via
http://www.facebook.com/aeroclub.phoenix.brueggen or
https://de-de.facebook.com/segelflug.elmpt .
They try to save Javellin Barracks as Airfield and had some special permit for extraordinary glider start and landings. Maybe it is still possible to get a one-time permit from Dusseldorf? (As long as these bloody windmills are not built on the field ... last time I was there - by car -, the runway was still intact and usable.)