You don't have to shim Mugen difs, as a matter of fact, there's no room for shimming the difs on the 5R or 5T. Do yourself a favor and get the oversized dif o-rings from A Main or Carolina's or Tony's and use them. Also get a tube of Mobil 1 synthetic grease to put on the o-ring and the outdrive during build up. Also I and a lot of other guys are using the non-prospec chassis braces (the plastic ones), the seem to be working better and will help in preventing the body from cracking along with making the holes in the body egg shaped. Start with the Scott Hughes setup and adjust from there. Scott has a very aggressive driving style and runs strapped, but the setup is great. You may want to reconsider you servo choice, the HS-645 for throttle is quite slow and may not give you the response your looking for and on steering it might be a little weak and could burn up quick. I think Monkey Wrench was running that one and burned it up on steering.