OK, I just remembered that I still have a MK2 camera.
I tried the MK2 + RRS L-bracket + lever clamp and it works well if the camera is shifter a tiny bit in the L-bracket to provide clearance for the cable release.
I then tried with the RRS Pano clamp (screw type) and the fit is the same.
I attached a quick snapshot of my camera, vertically mounted, with the cable release. The clearance between the clamp and cable release is maybe, maybe 1mm.
Hope this helps.