I've been in TT's that had a separate bunk room (Keystone Outback, bunk room up front, big bed in rear slideout) but haven't seen it in a fiver. Of course there are hundreds of fiver floor plans I've never looked at, someone might be making bunkhouse fivers.
Thirty foot length or so, you should find a lot of bunkhouse models in brochures, but tracking one down used may be difficult. Nash/Arctic Fox 32D, old Jayflight 31BHS, Rockwood 8317 all had bunk rooms with 4 to 6 beds. That's just three old brochures I had at hand, but most of the time, each manufacturer is making at least one TT like this. There is a market there, large families and youth groups.
