The expensive way to do this is with something like the Optec Libra. It carries my TEC140 but I had to modify it to eliminate a little flex. I've found that just rotating my cameras is enough to move the centering enough so that I'm not happy with the alignment of the two FOVs. Consequently, I'm happy to have the Libra because a simple "bolt and forget" solution wouldn't be accurate enough.
http://www.optecinc.com/astronomy/libra_dovetail.htm''
http://www.pbase.com/prejto/image/160559467
Peter