I designed it myself last year because i ran out of funds for a posh cage. Basically i bolted a framework of angle iron to the floor with rings bolted to that for two five tonne ratchet straps running front to back (layflat tank). I did the same with a lower rated strap accross the tank too. Problem was i only bolted to the floor even though it was in some fairly strong areas. The garage beefed it up for me by bolting into the chassis members too. Cost me £80 for the extra work. If you get under a Despatch you will see it's quite a complicated floor pan and quite difficult to get to the main chassis just where you want to with the fuel tank sitting under the ideal areas for the front mountings. I'm amazed so few people have posted on this and explained how they did it exactly. I can only think there are a lot of bodge jobs out there. Interestingly the garage mentioned how little holds a towbar onto many cars out there.