Help with set-up

[mustbnitro]

I'm about to place an order for all of this, the esc is already on its way, now I am going for the 9XL, MM ESC, and CC BEC, also I am springing for the RCM heat sink clamp, or is that really needed?

My question is, should I go for the RCM
http://www.rc-monster.com/proddetail...WAND_XL&cat=20

Or is this what I am looking for:
http://www.offshoreelectrics.com/pro...prod=fei-540XL

I am confused between "xl" and "XL", I don't want to drop some money and have the wrong motor show up.

Also, is the RCM heat sink clamp needed, or is there a mod I can do to keep the can on?

Can I run 5S on the MM, or should I stick with/ be fine with 4S?

I am running a 46 tooth spur on the truck, what pinion should I run for racing and what for speed? I am needing a pinion that fits the Feigao/Wanderer shaft.

Thanks for all of the help again, pics will be up when the truck is done, which I am trying by mid January.