Thank you for all of the great information! It looks like I am going with the 1515 1y, just because I will feel better with the larger can. Does anyone know the exact length difference in the 1515 and 1512 cans? I will get the 1515 1y test it on 4s, and if that is not enough I will boost it up to 6s. I hope castle comes out with their motors soon.