I had one. Very thirsty though.
I just had a 250l lay flat in mine. Im sure it would take a 400. Anything higher than that would be close to going over the pay load.
The 2 side loading doors are great!!!! Take the hose out of either.
Engine under the seat is a pain.
Overall not a bad van.
I got a transit swb now with a 650l upright tank. Only 1 side door