Asked Teilo for a Stako full centre filled 4 hole toroidal tank, with valve plate, part No F65007714L 65cm dia by 27cm high 77L= 61L useable, and he came back to me with an equivalent GZWM he said it has marginally less capacity due to the valve plate being slightly more recessed,and gave me a price of 278+20del+vat, with sender, valve set, vapour sealing box, filler, fill line, adapter for 3/4 unf to 8mm compression. I asked Lazy Docker and he said he thought it was ok and at a good price,I will of course need to build up the rear floor. My only reservation is the weight of the tank according to the shipping weight is 44KG still the spare wheel won,t be on board, if needed I do have an excellent fall back if the rear end sags unduly with the van in tow.On my previous MV6 miggy I had cylindrical pump up air bags that fit inside the rear springs and still have them, I fitted this system to preserve the MV6 suspension in solo trim and yet be able to tow, it worked very well, much like the present S/L shocks only it gave the springs themselves extra pneumatic support to maintane level according to load.Can't see me being able to work out all this tech stuff easily by myself Kevin,no doubt with lots of time and research I would eventually get there, if I get stuck your help will be much appreciated seen the pics of your install,gave me a standard to work to