Right, you're asking about rackmounting the ribbon controller itself into 1U, not the module it connects to, which is staying 3U and 8HP.

I just had a quick look though, and the ribbon controller is slightly longer than a 19" rack is wide, so I don't think it's going to happen. A shame, as on the other axis, it is thin enough to fit the 1U rack height. (You mention cutting it to fit, and I have no idea if it works that way, sorry.)

Someone could hypothetically make a 1U ribbon controller (say, with 1V/Oct and gate out, so it's compatible with more than just the one Doepfer module), but I think it would need to be designed that way, rather than cut up. I don't think there'd be much demand for one, and as a one-off it would be quite expensive and/or time consuming to build.

I'd settle for having the ribbon controller in front of the rack, on a desk. It's more comfortable at that angle, anyway.

Sorry I couldn't help!