I think so for 3.5T - as you have all that extra metal to carry in the body rather than be useful load weight
Have you thought of it (pole) going over the cab? - you might find a LWB plus the extra overhead compartment may get what you need
Darran
Got a transit l3h3. Tried measuring it at sorts of funny angles,😄, couldn’t get 4200mm.
Thought about a trailer, but we work away and leaving kit unlocked on a trailer at travelodge etc….
Got to be a jumbo type thing.