1.best bet is to make sure your fittings are good - well made.
2.make sure the tank has some form of collision defence - ie brace bars around it if possible
3. you can add foam to the inside to soak up the fuel - if it did get split the foam reduces the speed the fuel comes out - reducing the chances of explosion etc
4. you could get a plumbed extinguisher fitted - a hand held one is ok but it MUST be fitted in a bracket securely
5. finally make sure you can get out in 10 seconds flat (if i remember rightly the time set for drag drivers to get out saw it on the tv at bonnville or summink - might be wrong tho - lol
)