I use a Pegasus UPB for all my USB, Dew heaters and Power. I have the Rpi4 and UPB mounted on top of my scope on a losmandy plate. I just run one power and a USB cable down to the the mount for control.
Its a shame they removed the separate USB connector for the iPolar. You have to connect to the main USB connector, you cant use the USB connector on the saddle (well I can't!). I do exactly what you suggest. Before I start my session I bring out my MacBook (or windows system) and plug it into the PC connection on the Pegasus UPB, this seems to work more reliably than plugging my Mac directly into the GEM45, I think this is an incompatibility issue between the Mac USB and that on the GEM. You should be able to plug you Windows laptop directly into the the main USB connector on the mount.
It would not be that difficult to make a separate USB connection on the mount for the iPolar. I may actually repurpose the USB connector on the saddle and connect it directly to the iPolar as I don't use it now anyway.
WO ZS 61
Edgehd 8 with Celestron OAG
Stellarmate on RPi 4
294 mc pro
224 planetary cam
174 guide cam
Sesto Senso focusser
QHY5II-Mono guide camera
EOS6D - not modified
I was using the iEq driver for my GEM45, make sure that you are using a USB2 port and serial connection speed of 115.
I have been updating the driver for PEC and needed to update to the latest firmware, because of some extra firmware commands that i needed.
The iEq driver, which is the default if you select GEM45, will crash with serial connection issues.
I have switched to iOptronV3 driver and it works pretty well. I have moved all my PEC code to the V3 driver and all the commands work ...
Anyway, i suggest that you use the latest firmware and on iOptronV3 driver, serial is at 115.
For those that are interested in testing PEC, please see my thread and fork.
iOptron v3 PEC
Christopher | Sussex England | n2042.blogspot.com
iOptron GEM45 | Altair Mobile Pier | TSPhoton 154 @ F3.7
ASI 294MM Pro | ASI EFW | ASI EAF | ASI 120MM
Mini PC | Quad 4GB 64GB 5G | Juice USB Harness