I thought I had found the perfect 4WD chassis for Minion 1. It looks almost identical to the 2WD chassis I am currently using. Then, I take a closer look at the New Bright Rhino, and see that it is skid steer. Hmmmmm...
How did you expect to turn a 4wd platform?
Were you hoping for wheels that actually turn? Is not your 2wd platform skid steer as well?
Time to attempt to get my foot out of my mouth. 
I looked at your robot post after I replied here. I see you are using what looks to be an RC rock climber chassis. Steering wheels that are also driven is not a cheap endeavor. There may be something for you in the 3d printed RC vehicle that is shared via thingiverse.
The original chassis is two
The original chassis is two wheel drive with ackermann type steering.
I thought about using my
I thought about using my Maisto Rock Crawler, but it is too small. It was four wheel drive and two wheel steering, so I bought another and combined them to have four wheel steering, too.
I await arrival of a 4 motor controller.
What ever came of your 4 motor controller?
I ask because I might be able to help with that.