How do you use it to compose panoramic shots when you can't see the full image circle. That's my worry. The Cambo viewfinder is not as good but you can see the full image circle and than guestimate the amount of movement needed as a starting point. I just think the main plus about the Arca Swiss viewfinder will be it's biggest drawback when shooting panos
When I was learning to shoot 4"X10" film panoramics, I'd carry a little cardboard mask with the 4X10 ratio cutout. Moving it away from the eye was a representation of longer focal lengths, moving it closer to the eye simulated normal focal lengths, and up to the eye, wide angle. With experience it became easy to use and I'd know what to select - 450mm, 300mm, 210mm, etc.
Now working panoramics digitally, I'll choose focal length based on the vertical aspect I need to capture. The Variofinder can be handheld for making focal length and composition decisions (very useful off camera for technical scouting days).
I begin with the center frame and make any minor adjustments to fine tune. After I'm happy with the center, I'll capture the left and right by shifting each direction. I usually shoot 3 frame panoramics so I have ample overlap. If I'm working with fast moving clouds in a scene, and a focal length longer then 47mm, 2 frames are enough overlap (one shifted all the way left and one all the way to the right) I'm sure Enda knows this part, but for anyone new to panoramic stitching, the overlap needed is dependent on your DB sensor size, and the amount of movement your lens can handle. For landscape and architectural subjects, I almost always use either rise or fall plus shift to make panoramics. The all in plane movements, all made from the rear of the Arca Rm3di make stitching almost error free. I use the reposition method in Photomerge Photoshop CS6 (works great in PS4 and PS5 too).