Motor Mount Advice

I am currently designing a motor mount type thingy for use in my robot.
The mount will technically be for a power wheels gearbox (Provided in the sketchup file)

The idea is the mount clamps the gearbox onto a non-moving rod that passes through the non-moving portion of the gearbox and also affixes the gearbox to the provided framework.

There are 3 rows of holes on the frame, the middle is for a right angle bracket for the main body to attach to the track assembly and the top row can be used to mount the gearbox to.

I am trying to just mount the gearbox to the track frame because there will be compression springs between the track assemblies and the main body so space is a tiny issue for the mount, but I am open for discussion about it. I can possibly flip the right angle bracket to open up more space if need be :)

Thanks for any advice, sketchup file is here via Dropbox https://www.dropbox.com/s/svq6qn0v17...acketScrap.skp

Hmm, sounds really complicated. May I ask what the robot will be doing with all this?