The C8 uses a moving primary to focus, so the mirror could shift and flop during focus and when the scope change pointing position. So when I flock my tube, I also installed two aluminum plates behind the primary mirror cell, and two screws in the back to support the mirror. I also installed a Hutech SCT focus lock to replace the main focus knob. These enable me to use a guidescope piggyback on the C8, and I only need to focus the CCD on C8 with any bright star once in the night (except I change the optical configuration, as temperature usually doesn't change much overnight here) and slew anywhere without loosing focus (unless pointing downwards).