Oh man - That is a real downer about that spur gear. I'm so glad you are posting all of this because it's nice to see everyone's feedback for when I start my project...speaking of which. Guess what I happened to track down at one of my LHS's? :027:
I scoured the internet looking for one and hear it was in my back yard!
I know Brian already showed his next to his Jato but here are some more comparisons:
Next to it's big brother CRT
And an 18t, GT2
Like Brian I was thinking about a MM4600 or 5700 too but it looks like there are quite a few issues to work out with the metal spur and finding a 1/8 in bore Mod 1 pinion. Anyway, just some other thoughts:
Again just for size comparisons. Here is a Feigao 7XL and Maxamps 3S 4000 mah pack in place