Hi!
For spec-r you need also sterring block from yokomo but it fit really badly,
so if have cnc drill flat bit 10mm you can prepare ae block
Outside bearing is 5x10x3 which come with spec-r axle, inside bearing can be 5x10x3 or 5x10x4 but it need go more to plastic, so you need cnc flat 10mm bit to made deeper hole.
Then use hex from hot bodies cyclone, don't use yokomos hex, I get one,
and it has to strong allu, it break on small screw, so it sucks ... (expensive crap).
Anyway, it is possible to do this mod but need some tools.
Regards!
m.
ps: my movie:
http://www.youtube.com/abrampl#p/a/u/2/7S4OU97CN7c (there was bad url, to another mod)