Trucks under 6m

[phoenixsp1]

Hello, I've just started looking at this site as I'm becoming very interested in building a camping truck.

I've been reading most of the truck threads and most of the trucks seem to come out at around 7m, I'd preferably like to keep the total length under 6m if possible. Is this going to be possible and what sort of trucks would I be looking at and what would the maximum length of my camper box be?

I was going to go to Withams and have a look sometime this week just to get a feel for things. I'm a bit of VW nut so like the look of the Man 8.136s but the only ones I've seen for sale are on mobile.de and they seem to be a bit pricey. Is there anywhere else I can look?

Also can anyone point me in the direction of any good sites which offer advice in building the camper box or possibly designs? I was thinking of using steel box section frame and ali sheet to keep things simple. I'm not sure what thickness of box section I should be looking at?

Last question, if I bought a flat bed truck and mounted the camper box onto that would I still need a torsion free mounting or does it depend on the truck?

Thanks in advance.
Clive