I was about to go that route, but I figure that it is cheaper just to get the Kyosho plastic spur gear for the Inferno diffs to go on my Hyper 7 differential. The plastic spur gear should only cost ~$5-7, and can be ordered from Kyosho directly.
I've had several different motor mount styles.
1st -
http://img.photobucket.com/albums/v1...r/IMG_0682.jpg
Uses the stock differential mounts on my XTM X-Terminator. 1/8" thick aluminum wasn't enough.
2nd -
http://img.photobucket.com/albums/v1...r/IMG_0742.jpg
http://img.photobucket.com/albums/v1...r/IMG_0742.jpg
Then came the custom mount. This worked, but my battery space was limited and not very stable.
3rd -
http://img.photobucket.com/albums/v1...r/IMG_1045.jpg
http://img.photobucket.com/albums/v1...r/IMG_1059.jpg
Another custom job, with a custom chassis as well. This chassis worked decently, but I ended up ditching it for a single pack configuration.
4th -
http://img.photobucket.com/albums/v1...r/IMG_1698.jpg
http://img.photobucket.com/albums/v1...r/IMG_1693.jpg
Again, custom. This was my most recent configuration. Worked well, but my newer setup (that I am still working on) uses two packs.
5th - no pictures yet, I'm still working on it. It uses the stock chassis, and batteries will be mounted using velcro holding them to pieces of 1/8" thick Garolite securely secured to the mud guards. The motor/differential mount contains a Hyper 7 diff that will receive the Kyosho plastic spur gear. The motor is above the differential, due to a lack of chassis space. I'm even having trouble figuring out where to mount the controller!
So, I know this is more than what you asked for, but these are some ideas for you to think about :).