Castle 1415 suggested gearing

I stand corrected, my apologies :) IIRC I had seen an earlier post where he said they were going to be the same, but doesn't look like that ended up being the best choice. quote from Pdelcast

Nno -- we used a little different rotor in the 1415 -- it's a little smaller in diameter than the 1515 rotor.

It was more expensive for the tooling, but we got better performance.

So they got better performance from a smaller rotor. Interesting.

aus, something else to consider with that gearing is the esc. Could be they are using the MMM with the 2650, and the MMP with the 2400. Though they still seem quite lop sided.