nah i'm afraid i dont agree with that glyn, I've heard suppliers say that line before and it is the biggest cop-out ever. So your solution is...to do nothing then? To rely on the fact that some guy had a crash and it seemed to be ok?
If you crash your van head on into a solid wall, the strains that pull on the system are gonna basically the same no matter what the make of van. A head on crash is a head on crash.
And as for the tank sizes, I you couldnt test a 300 litre tank and say we'll use the same design for a 1000 litre and it will be ok. BUT, you could do it the other way around. What I mean is if you tested a 1,000 litre system and it was all ok, I think it would be ok to say right, we'll use the same design, clamps, and install procedure and steel and everything as we did for the 1,000 but we'll only use a 600 or 300 litre tank. To me that makes sense. If it held up for the bigger system, it will of course logically be ok for a smaller system.
No offense but both of those arguments are what people say when they basically have no argument at all. I had a very close look at all the systems and things by various suppliers before i bought mine, and what I saw is that nearly everyone is claiming some kind of safety, but always based on just nothing really, but it seems to me that they feel they have to say something.
For example : "installed by professionals" means nothing does it lol. "installed to ministry of transport standards" ministry of transport doesnt even exist anymore. "installed to the highest specifications" lol meaningless. "Professional factory fitted" Lol does the fact it was done in a factory make it safe eh? It shows that they are aware of the danger but are doing basically nothing about it except coming up with good sounding phrases, probably as you said because its too expensive.
I notice that essentially pure even sell their systems for the customer to fit himself! LOL Totally irressponsible that is in my opinion. Can you do that, knowing the risks involved and still claim to hold life as valuable? Personally, I dont think so.