RE: Steering problem
The multiplex rhino is plenty big enough. Are you using a "Y" harness to bypass the battery power past the receiver and straight to the servo? You can also upgrade your steering linkages to the aluminium ball bearing type or just keep the plastic ones clean and lubricated. You can spend the coin on the modified "tonigawa" (spelling?) servo but I don't think it's needed.
Have you ever driven a car without power steering? They are a pain to reverse park but once you are rolling there's no problem.
I have been running a Rhino for over two years. It's a great servo and still going strong.
HTH. JIMBO.