Unfortunately there is no option to CAT control the SDR-4+ in CW Skimmer. Usually you would look for a SoftRock Ensemble option as it uses the same Si570 controller.
One option is to use the CFGSR program to set the SDR-4+ frequency then enter that frequency in CW Skimmer as if it was a fixed SoftRock receiver. You can't tune around with it though.
It motivated me to design the controller for the Sentinel 2 receiver (and also the new Sentry 5 transceiver). It can take CAT control commands to work directly with CW Skimmer. You can also use any suitable digital mode program while using the Sentinel SDR program just as a receiver front end program processing the RF signals to audio.
Regarding my vision, it's fixed now, thanks. I've cut back on the amount of programming I do now but it doesn't look like it looking at my desk this evening as I chase the last bug in the Sentry 5 firmware!