The problem is that with the USB3 connections in the mount (both ends) you get quite a bit of loss and the USB3 specification is very limiting. So the remaining cable length is very limited. What you need is a usb3 driver as close to the bottom mount entry point as possible. What works for me is a 6" usb3 cable connected to the input of the mount RA axis, with a USB3 repeater cable from there to your computer. My repeater cable I have is quite long and the repeater electronics are on the mount side (female side). So you basically have a USB3 repeater/driver 6" from the mount. For me this has been very robust and you'll find it not very expensive.
