!!HELP!! Gearing and the Jammin x1 CRT Truggy

[Mentat]

Guys, just wanted to know if there is anything special i need to know when gearing this Truggy? im currently using a 46t Spur and 13t Pinion 4s1p lipo. With this gearing, its saying i can get 48mph, I decided to drop it down to a 10t Pinion and get 38MPH, is there ANY problem running a 10T RCM pinion with this Truggy? If im not mistaking doesnt this Truggy use 43/13 front/rear diff gearing? I know that most truggies use 43/10. This truggy also came with a 62t Spur to start, and its just way to big, so its why i went with a small Spur any probs doing this?. Also doesnt the JAMMIN Diffs need to be Shimmed? I took apart the center diff and seen several shims I just dont want a busted drive train. Lots of INFO needed on this issue, thanks!