Tennet - no offense matey but this is MY area of expertise, I am an engineer (no not someone who fixes dishwashers - an engineer,a real one).
Ionic Systems tanks are completely generic, your point about if the 1000ltr is safe then the 300ltrmust also be, makes total sense, only if the frames used are the same for the 1000ltr and 300ltr, I suspect that they are not although I could be wrong. In a head on collision the major points of failure are likely to be the base mountings, the forward face of the frame and the rear floor bolts (as the tank will inevitably try to lift from the rear). Now lets assume that the tank is fitted correctly, which is through the chassis legs with HTHT (heat treated high tensile) bolts, which are fitted through spreader plates onto the bottom of the chassis leg, the top half of the bolt also needs to be fitted through a spreader plate on the frame - if Ionics have another means of fitting them I would like to hear about it.
Now we have a frame fitted through the chassis legs with spreader plates, the frame has been well engineered to displace load and stress, the frame has been manufactured to standard as well.
Will this one design fit any van - of course not! It needs to line up with the chassis legs correctly on every van, it wont do this, so how do we overcome this problem? Answer there is no real way to overcome this other than specific frames for specific vans, no one does this.
Tennet - take a look under your van and tell me if the spreader plates are fitted to the underside of your chassis legs - in all likeliness they aren't.
Tell me, what does FMVS testing actually prove? Does it prove that the tank will stay in place in a 30mph head on? What about the increased momentum of my vehicle due to it no longer weighing 2ton but now 3ton - how will the crumple ones perform, what about the passenger compartment cell?
If I am wrong then I am wrong - I have never inspected a fitted Ionics system, I have only looked at one sitting out. They look a good system, don't reckon they are worth the money but thats none of my business.
I think I will start designing and manufacturing my own frames, there are a number of key engineering issues that all the manufacturers have missed out on, obviously I'm not going to mention any now.