Not sure but to be honest mate its not a good idea

If the vehicle ever gets a heavy shunt up the rear the floor around that area will buckle very easy and chances of it fracturing the tank are high too. Bad enough being in an accident but then finding out you have fuel leaking everywhere could be a nightmare.

I was left with a similar dilema when building my car so I removed and plated over the wheel well, and after chopping out a space for the extinguisher and battery made a steel construction framework for the homemade alloy tank. Its safely out of harms way inside the roll cage area should anything ever happen at the rear Its stepped down in the middle to create a low spot where the pick up pipes are so no matter what type of corner im going round there is always a head of fuel in there



Finished with a fiberglass lid and all the expensive aeroquip it works well Keeps the weight central too



Big job though..... so would you not be better just fitting a return swirl pot and taking the feed from that ?