I also forgot to mention that if you do not have a (.10sec) servo or faster,cranked up all the way, it will be very difficult to turn,,,and if you run a front diff the inner front tire will not brake in a turn, making it hard to snap the rear end around tight bends....I only use front spools from now on, and another advantage of the spool (when running very low front droop) is that it takes off a lot of pressure out of the rear diff ,therefore eliminating rear diff wear and slippage forever. I have built my tc4ft 3.5r in 2005, and I never rebuilt my rear diff since; it's still butter smooth and holds when I tighten it.....When I first built it, I used front diffs for less than a month, and could not solve diff slippage and diff bolts breaking until I switched to front spool with LCds only.....Anyways good luck with your tc4s giys......