The stupid ECU doesn't quite fit between the frame bars so I need to mount it high enough so it will fit. I can then use the space under it for the battery connections and some other electrical bits like the indicator resistors etc. The original ECU supports had AV mounts so I guess I should do so again, although the whole thing will be mounted upside down. I made up a plate which will hold the ECU over the new tray with enough space under it to accommodate the other electrical bits. The seat will be mounted higher than the original so I have a plate each side to infiltrate the gap between the frame and the underside of the seat.