I've been getting back into ATV and Satellite work after some time

I have successfully installed the Portsdown 4 system. I unfortunately do not have a touchscreen. However, I do have a PiKVM (https://pikvm.org/) which is a device that uses the camera connector on the Pi to let you use your Pi as a remote KVM server with an HDMI input.
I thought, well since it uses the camera connector, would it work with Portsdown pretending to be a PiCam? And low and behold...it works - nearly!
I'll send through a picture in due course (not at my equipment at present) but basically the picture on tx is the right 50% of the screen (I was sending in a 16:9 source).
Does anybody have any ideas how I could maybe tweak some picam settings under the hood of portsdown? It must be able to work correct somehow, the folks at PiKVM do it.
Thanks
Jonny MI0MTU