This light weight but rigid motor mount allows for unlimited adjustability for gearing options and also allows a much larger pinion than stock. 

Currently I am using 64 Pitch gears -  A 84T Spur, and a 57T Pinion for a FDR of 3.83 on a 13.5T motor which results in a very fun setup, perfect for my local track.

This part has only been tested it in the FF configuration of the BT-01.

Using the stock mount, the smallest center to center distance you can have between gears is 27mm. Although this mount allows for 26mm, I don't think you can go that small because the motor will hit the plastic chassis.

Using the stock motor mount, the largest center to center distance you can have between gears is 28.2mm Again, I don't think you can go much bigger than than that before your motor will hit the plastic chassis.