I ran into the same problem when I put in my 10L, I had to go with a 16T 5mm pinion. It just barely fit but it runs great. I was surprisd that the axles held together with BL power. I'm going to buy the Dragoon chassis when I get some extra money and self the Stealth one.
i'd love to make this thing brushless - but it'll require 2 complete systems. and the minute i save up for that, a company will figure out a way to make one controller that can utilize 2 brushless motors. (doubt that will come to fruition, but stranger things have happened).
so do you have two 10L systems in yours? are they each paired with a MM? and why are you shelving it for a dragoon?