You might try this if the FX8 can be used in the loop. Have one main Mark generate your tone use your effects loop to generate the stereo. Effects loop send to the FX8 then send one side back the the mark that is your main and send the other side to the second mark effects loop input. That is how the tech at Boogie told me how to setup a stereo rig with two mark V amps. Basically you are using the second mark as a power amp and speaker. I could draw you a diagram if you need. This way one Mark V runs the show. Simple no hassle. You could just put a stereo chorus pedal where I put the FX8. Then you would setup your system on the first amp like normal with your FX8 and Koko boost.
I tried full stereo with my Mark V and to me it sounded mushy. I love the 2x12 vert. cabs as my main tone. But when I put the stereo chorus on them the tone was gone. So I added the second set of 2x12 compact cabs.
Here is mine. It's not a standard stereo rig as only the bottom cabs are stereo but it sounds awesome. Everything on the pedalboard stays connected. I just place the cabinets, amps, set the pedal board and grab the cables walk back and plug them in. It's worth the work. The delays are in the loop, CabClone using the speaker emulation to the strymon chorus and reverb are the stereo lower cabs. With the cabclone I use the speaker emulation as the line out was not what I liked tone wise everything else is in front of the amp. I use 2 hum eliminators on either end of the line going to the pedal board, odd but it did the trick ... I have no hum. The two 2x12 vert cabs are direct from the Mark V.
