OK....Kevin you asked for it..... this will be long but very infromative...
First you need a Schematic or Drawings of what you want a Fuel Cell company to manufacture for you.... Here's an example
Then you need to design a Collector... inside the fuel cell for a couple of reasons .... one for a reserve.... but also a collector is used to capture fuel from the corners of the fuel cell.
Next you get the fuel cell in then you have to start modifying.
Here's the Passenger side of the cell which has the Fuel Level Sender and the Vent Check Valve for roll over.... also the same Vent is on the other side of the Fuel Cell. When fuel cell is full and you go around a corner one of the vents will be open ....
