Try to see/feel one of those tanks before you spend the money. I had one in a corolla race car and it always felt like nothing more than a think plasic milk jug holding flammable liquid....
If you do decide to go this route, make sure it is strapped down very tight, very well supported, and not resting or rubbing on anything sharp. Also if it was me I'd pull it out after 6 months and make 100% sure it's not wearing weird anywhere, then if it looked good, take it out about once a year after that. If the brackets are built right this should be an easy task.
Buy some of the fuel cell foam if it doesn't come with it, as it will help greatly reduce fuel sloshing which will help keep the fuel going to the pump.
I like the idea for a cage around it, although if done wrong it may just become the sharp object that punctures the tank...