The system was made for 1/16 size. The motor also has a 1/8" output shaft so 1/10 pinions gears work on it. I have one in my Vendetta Short course truck and it does well, however you must gear it right.
http://www.rc-monster.com/forum/showthread.php?t=28823
Check this out:
http://www.teamnovak.com/download/in...ngoose_ins.pdf