We have started using this really affordable encoder ($5).
http://www.bgmicro.com/index.asp?Pag...D&ProdID=12916
After testing with the cRio, this Oak/Grigsby Encoder performs at the level of the Grayhill 61R
We mounted the encoder on the CIM with latex tubing connecting the drive shaft.
http://picasaweb.google.com/LamarRob...45261834041890
For more pictures of the mounting scheme, check out our photo gallery,
http://2009.discobots.org/node/34