Laco, I think going from 80 to 90 inches would be huge for a van camper.
A lot of small motorhomes are 90” wide, like the Winnebago Via/Reyo Class A based on Sprinter chassis, and the Thor Gemini, etc. There is at least one B+ on Ford Transit that is 87” wide (Sunseeker).
In Europe many motorhomes are 88” wide (2.25 meters) and they work fine, so we can get an idea from them.
Regarding wider vans, Mercedes had one that was wider than a Sprinter. I’ve seen pictures of motorhomes built on that platform and they were very roomy by comparison. Even today the extra 4” between a ProMaster and a Sprinter is significant.
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