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.

Hello

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

Just received my GEM45 and got no connect!
Then I just changed the port speed to 115200 and then it connected OK! Probably should be set by default to that.

I'm on powered hub. I'll try to change it to directly at RPi....USB3
No! It even hangs the SM, cannot disconnect!

Trying on unpowered USB3 HUB No! Does not work!

Trying now to set it back to powered USB3 HUB... No! not this time...

Restarting all with GEM45 in powered USB3 HUB ... Looks good at speed 115200 baud Problem solved with powered hub.

Will now try out the GEM45. So far found that my ZWO EAF hits the saddle and I had to remove it until I can find some raisers to get it above the clumsy box not containing the IGuider.