Interesting Subject
This subject is the one that gave me the most heartache in the build of my truck.
There are many ways to build a camper, and everyone will tell you you are doing it wrong if you didn't do it their way. After boatloads of research this is where I ended up.
Unless you want your camper to fall apart you have to put some kind of mechanism in place to prevent the camper from twisting with the truck chassis.
To answer your question, all of these systems will have a hard mount point at one end if properly built to conform not only with the body builders guide, but with the law.
There are three basic systems to do this.
Spring mount.
Rest the subframe for your camper on the truck using springs all the way down the chassis. This was designed for tanker trucks to prevent torsional stress transferring to the tank. This is how earth cruisers are built and they have had great success with this system. This is a very light, elegant, and simple solution. I think that careful research into the stiffness of the springs is important to try and limit chassis flex. If you attach the frame solidly to the chassis at one end as you pictured in the body guide it will still flex the same amount. (Think Dumptruck)
3 point mount.
Firmly attach the camper at two points at one end and make a pivot in the center at the other. This system will not work properly without a subframe underneath it as it allows unlimited chassis flex and concentrates all the weight of the camper onto the three small points on the frame.
4 point mount.
Mount the camper on four pivots. One front and center, one rear center and one one each side in the center. When viewed from above they form a diamond shape. They must all be in the same plane to work. This is the system most often used on Unimogs. Once again, a subframe underneath is necessary to prevent excessive chassis flex and spread the load.
The chassis is made of very flimsy steel and therefore the truck frame twists a lot. The builders guide states that you must build a subframe and bolt it in place. I believe they designed the chassis with the idea that there would be a full length subframe adding rigidity to the the truck. This is what I did. I built a full length subframe which is firmly attached with many Ubolts per the body builders guide. It has a plate at one end bolted to the frame of the truck to prevent fore aft movement. I then built a 3 point mount attached to this subframe. With a full subframe between the three point mount and the chassis the weight is spread out preventing single points of stress. This also prevents excessive twisting of the chassis.
The best known case of three point mount frame failure was with a truck which had an extended frame and was way over weight. I discarded this as an example when making my decision as these two factors are adding significantly compounding stresses on the frame.
There you go! One more opinion in the multitude.
Take care,
Allan
