Good call on the pinion Dave. I like the align pinions and you can get a set of 3 or 4. I got mine from Michael @ UsHobbySuppy.com or maybe you can get them from a LHS. I couldn't find them on the BP website. The Shaft diameter on the E-Sky 3800 ( part # EK5-006) is 2.3 mm.
Dave, that dude is crazy[&:] I'd fly it at least once before giving it back
Blessings,
Jay