This is my setup.  A Vixen R200SS 8" f/4 newtonian telescope on a Losmandy G-11 mount.  The guidescope, a Vixen 90mm f/11 achromat,  rides piggyback on the R200SS.
 
 

This is a close-up view of how the guidescope is mounted on the main OTA.  The green rings seen in the picture are the stock rings supplied by Vixen for mounting the R200SS.  The long black plate is a Losmandy Universal Dovetail plate (DUP) that mounts on the holes on top of the Vixen rings.  Two Losmandy DR125 adjustable 3-point rings then mount onto the dovetail plate and are used to hold the guidescope.

Here is another view of the adjustable rings and the refractor mounting.

The R200SS mounts on the G-11 saddle plate using another Universal Dovetail Plate from Losmandy.  This bottom dovetail plate is attached to the Vixen rings using the holes on the bottom part of the rings.  This is symmetrical with how the dovetail plate is mounted on top of the Vixen rings (see image above).

This is the focuser on the R200SS.  You can see the locking screw on the top of the focuser.  This focuser is rock-solid and does not move once it is locked down.  There is no play whatsoever in the drawtube and rack-pinion mechanism.  The black flange seen attached to the focuser is the Vixen Direct Wide 60mm photo adapter.  This accessory is not a necessity for astrophotography but is nice to have since it considerably reduces the vignettiung caused by the stock adapter that is supplied with the R200SS.  One added advantage of using the Direct Wide adapter is that it also incorporates a camera angle adjuster.  The black bracket seen screwed into the tripod hole for the OM-1 camera is used to hold the B&K astrofocuser, a focusing accessory.