After all this talk, gotta consider that the third seat floor space is very shallow, but lots of length and width- the worst form for a fuel tank. I think you'll need more depth to pull fuel without consistantly sucking air. No real "low point" either. I'd put the WVO in the main cell and either replace the spare tire space or the jack/first aid kit/rear wiper fluid area with a fuel cell for diesel. You could then plumb it to the sealed third seat floor space tank.