... Have to take care filling that with a hot engine.
Not really - all my motoring life I have run cars with scuttle fuel tanks. It's almost impossible to splash fuel when filling because the pump nozzle can be inserted well inside the tank, but if any fuel does spill it evaporates instantly when it comes in touch with a hot engine. The only danger comes if one tries to refuel whilst the engine is running and there is a possibility of sparks from the ignition, but anyone with common sense is going to switch off anyway ...