Thanks, and I agree. Unfortunately currently no 40 for sale in Belgium ...I have a 42 the same height as a 40 and there is plenty of headroom for my 6 ft son. When buying that was not the deciding factor the 40 is about 20% heavier with the attendant increase in internal volume.
Its best to visit a few to get a feel. I thought a 36 would suit me mest when looking at plans. There is no substitute for visitng a few.