This has been the biggest pain in the A*** so far on this car. In a nutshell, it doesn;t quite fit, it needed me to make spacers for it to provide sufficient clearance from the main prop mounted gear and it was sitting too low to provide vertical space between the two gears when they interlocked.
Started off expanding the mounting hole on the chassis on one side, as if fitting like an alternator, so a longer hole which would allow me to rotate the reversing motor and create a couple of mm of clearance.
Once i had opened it up sufficiently i created an extra spacer and then, with the prop now securely in place, refitted the reversing motor. ( I had to fit and remove this god knows how many times to get it right).
It now has about 2mm of interlocking between the two gears and when retracted, doesn’t foul the main prop gear. Will have to see when i move her for the first time if it still looks right.