They use the same ali cylinder tanks on a lot of the trikes too, never heard of anyone having any kind of catastrophe with them
I have sold at least a dozen of them through kingfishers, and trust me - i wouldn't sell them to a hairy arsed biker if i thought there was any chance of something going wrong with them
If anything, from a general maintainance point of view, it is gonna me much better to have the fuel tank mounted on the back (like on the buggys and trikes) cos at least then you can keep a real close eye on the fuel lines and it is gonna be a hell of a lot easier to spot a perished or leaking line.
But from a safetly point of view, a fuel tank is gonna be dangerous in a smash no matter where it is placed unfortunately