Thanks for all the replies, certainly some food for thought.
That's good to know. So a competent builder shouldn't have any trouble.
Well I guess busy is a good thing, people must like them.
Yes, that event looks like an overlanders dream. I'm just starting researching before so I know what to look for.
I guess a high roof line is unavoidable then (except for lifting roofs which I don't really want to do). As it's not worth compromising on subframe design or tires just to lower the roof.
I have read about the MAN frame failures also. My conclusion is that most of the failures are through faulty subframe designs. Our engineers and other builders I know, are well aware of that and have adjusted to that. They have never had any failures.... knock on wood!
Ormocar has been building composite campers since the 1980s. It's their only business. Their design is definitely not fancy but solid and they have a lot of experience. As far as I know they are the only builder who is producing his own panels. When you order you can chose how thick the fiberglass and the foam core should be. I was very happy with the build and can recommend them if you have enough time. They are very busy and usually late. Just add a few weeks to the delivery date quoted by Ormocar.
You seem to be based in Europe. If you want to check out Overland Vehicles go to Abenteuer Allrad https://www.abenteuer-allrad.de/ . At the fair and in the camp area you will find the largest selection of Overland Vehicles and parts anywhere in the world. Everybody who thinks he is a major player in this market is there and you find more than 1000 overlanders in the camp area. Usually many used Overland Vehicles are for sale.
Height also depends a lot on cabin mounting system. A true torque free three or four point system ( depending on how you identify points) diamond shaped system is going to be higher then other systems that apply torque to the cabin. Also tire size. 14.00R20s are often used for lowering RPM and ground clearance but lift the vehicle 80mm relative to 365/80R20 and 40mm relative to 395/85R20. 14.00s and 395s have higher load capacity. 395s are easier to find because of all the military surplus (new) ones around.