i will try to answer mr bit and pw1 together
pw 1 this isnt an alternative for not having a frame this is the ultimate anchor system the likes of which window cleaners have never seen, let me explain,
we have only ever seen tanks bolted down transversly befor regardles of which supplyer and what the tank was be it framed or unframed ar any shape,
now this system is so flexible the track can run side to side or front to back or both
i work a bit diffrent to most of you guys i dont use the van system with hose reels a lot what i do have is two trollys and 2 hose reels and 2 backpacks the diagram shows this the red lines are the tracks the first yellow are the tanks the second are the trollys and last the hose reels if i want to use them all of these are anchored down and all can be removed in minutes leaving your van empty for other things you may want your tank at the back of the van for some reason or in the middle no problem just slacken the anchors slide over and retighten you may want to put a second tank in your van another set of anchors and your done no drilling or messing about