I did the following so I could use a shorty both ways without needing to change anything in the car. The side pods are cut with a couple of foam spacers glued on either side, the motor cover is raised a few mm and I drilled new holes for the battery holder. With foam tape on only one side of the battery strap, changing battery positions is as simple as flipping the strap over and moving the battery.

Please excuse the wiring, I quickly ripped the electrics out of another car to test this out.