I use them as thickeners.
The c9 I have on the swell setting, and b9 on fat Hammond for doubling a la Jon Lord with the purple songs we do
Occasional chords, but normally doubling what I'm playing.
I've found the best solution sound wise for me is to run the pedals to di, with a killswitch, rather than switching the pedals on and off, since there is always clean sound coming through even with the clean volume on minimum