Andy your van looks like the dogs whatsits to me> How did you fix your tank? thats the real issue here. I saw a bin cleaner with a loose tank in the back of his transit. Big mistake! in a 30mph accident a 500l tank becomes the eqivilent of about 20 tons of unstable load with you sitting right in front of it. Death if you are lucky, a broken back and life in a wheelchair if you are not.
At 50mph its certain death.
Tanks have to be secured PROPERLY, don't take chances.