I don't have the stock main gear but i do have the gear for the blade 400 which i got everything to line up and work with a touch of grinding with my dremel to the main frame just under the motor mount, it was one of the corners that i had to grind less then 1/8 of an inch to get the motor mount to slide in far enough to hit the gear but i got it to fit and every thing lines up good with a thicker washer inbetween the main gear and the top gear for the tail.

My question is the blade 400 one way bearing gear has less teeth then the stock one way bearing gear (not sure how many less yet) but will this change my head speed ? will it increase, decrease or stay the same ?

Thanks