Firstly I must apologise for my total absence of German language skills

Ive tried searching but the combination of a lack of language and the devestating effect web translations programs have upon meanings and syntax has left me clueless.
I have an ex-BW driving school 110-17AW, 1 wife, 3 small children, a bullmastiff, a nasty habit of racing offroad cars and the usual lack of money that combination brings.. so, time has finally allowed me to make progress and now I need to make a camper that will make everyone happy...
I have just bought a "box" which is actually an ex-prisoner transport unit, its a perfect fit for the 110-17's bed, its insulated, strong and well made. Our trips to Russia (and some of the more rural bits of Eastern Europe) mean I am concious of the need to isolate the box from the chassis's torsional flex, but the truck must drive well on the road as my wife will also be driving it.
the vast majority of the trucks time will be spent on tarmac. Russian roads may count as offroading but mostly because of the car sized potholes but they are generally flat, we will be parking offroad and that will mean some offroading down the logging trails and ditch driving to get to camp.
I am really interested to hear your thoughts and advice please!
1) my current favourite idea; the "spring clamp" method that is standard on these beds, Im aware of its limitations though so I wondered if it could be made more efficient with longer springs, longer "slider guides" to relocate the bed as the chassis twists and a reduction in the number of "inflexible" fixings, I could also add a panhard rod at the front of the bed if you guys think it necessary?
Questions; what dimensions would you choose for the compression springs? how much resistance should they provide and how to decide on thier length?
2) 3 point, obviously I would need to make a new crossmember for the front of the bed, I have read of effects this system has upon the vehicles handling
Questions; Is the impact on handling on the road very noticeable? I could use a cable operated disc brake on the pivot shaft of the front link to "lock" the bed for road use - would this cure the problem?
3) Hybrid; springs and a front link (effectively providing) a panhard but it would be possible to also incorporate the disc brake - I could then reduce the need for such strong springs in the clamps?
Im a mechanical kind of guy, working metal is not a problem but Im very new to trucks!!
I look forward to hearing your thoughts and advice and thank you in advance!
Cheers
Jez