Thanks for your answers everyone! Fiona Rogers was so kind to mail me a scan of the original accomodation layouts. There seem to be three versions. In all of them the quarter bunks are 6'6" long. Interestingly, longer boats do not generally mean longer sleeping places: I looked at a lot of 30 ft boats now and majority of them have bunks that do not measure much over 6'6". (I guess it is because I am only interested in classic GRP: old times, shorter people..). I may have to shorten my legs!
One exception so far is the Swedish Marieholm 26 which has quarter bunks of 7'10" ! The design is also based on the Folkboat. Does anyone have experience with this boat? It must be a sound design, the Scandinavian reputation being what it is. Some practical items missing: no toerail, no chainlocker.
Bert