Visited Oberpfaffenhofen (where the F?) about 35 years ago and recall several of Dornier's experimental aircraft on display outside - one was certainly a Do-31, not sure what else there was (one of the ex-Spanish SAR Do-24 flying boats rings a teeny bell)...
Edit: I see the Dornier display items are now at Oberschleissheim which opened a few years after my visit - pity, must go back some time!