If it will help people out there, I can add a section to my site that lists the dimensions of the shafts from various vehicles. That way, people can maybe find something that will work...
That's great idea. Just make sure it's measured the same way i.e. center of pin to pin.
Castle Neu 1520 on 6S LiPo Powered Gmaxx (Nitro Killer)
Predator with OS .21TM
Supermaxx with Mach .26
Revo with OS .18TZ
Kyosho ST-RR Conversion
Ofna CR with Tekin ESC/Motor (2)