Hmmmm - I just thought of something! These adapters may also work as a great fix for the couple older Eldon shells, that don't have the separate chassis - but rather, have the set up where the motor snaps into the body like this:

Somewhere in one of the boxes, I have a couple indy bodies like that where at least one of the ears is snapped off. It should be possible to simply glue the adapter in and then snap the motor into it I would think?
Now to find those bodies and wait for my adapters to get here! :D