No luck with the 7N0 Gateway and original PDC, so it looks like I might need to upgrade to the 1k8 PDC. Hopefully this also works with the 3C8 Gateway - I'd rather give up the OPS display than have to do everything else that required with the 7N0 Gateway.

Interestingly, I can't find anywhere that specifically says you need the newer PDC for OPS to work (unless, as mentioned in this thread, it's to enable the camera overlay). Even the stores selling retrofit kits mention nothing about OPS.