Sounds like a waste of money if you are going to bash your 18t. Honestly the stock chassis never broke, and I tried to break it. The diff situation will be a problem if you do not upgrade to the mip super diffs. Once you have rebuilt the stock diff a couple of times you will see. Just need a well lit room and a large shallow pan/dish to do the diffs. You also need to shim them correctly so the ring and pinion mesh properly. This is easy(well, easier than rebuilding the diffs!). Makes sure to keep a few sets of the diff gears handy as they wear out the fastest.
IMHO - if you have the $140 to spend on this, save your money and spend it on the xray. In the long run you'll spend more money on hop-ups for the rc18 and will just end up frustrated.
“Everyone has a right to be stupid; some people just abuse the privilege.”