1512 in a Rustler?!? Way too big IMO. I'd go 1509 2.5D (2700kv, non-finned)at largest, or maybe a Neu 1112 2.5D (2900kv) for a smaller diameter motor. And it turns out that the shaft on the 1112 is an 1/8" shaft!
http://www.neumotors.com/20061222/11...es%20data.html
SH Z-Car, Custom Crawler, 8s Savage,
12s XTM XLB 1/7 buggy,
4wd 4-link rear/IFS Pro4 truck,
Custom Hyper 10 Short Course,
Belt-Drive Mammoth ST 1/8 truggy, 4s 17.5 MM Pro HPI Blitz