Casale drive units were part of the original design for the E-Racer. They were basically a v-drive unit with parallel shafts with outputs on opposite ends. The pic above is of the inside showing the gears. The one below is the model that Casale makes that E-racer have used to modify for use as redrives.
I have NO IDEA how well they work in aircraft, but the v-drive drag boat guys love them.