It should work out of the box with UgCS. Please raise this to UgCS support and attach your vsm-ardupilot.log. There are problems with USB hubs, though. It can be that USB hub is not able to provide power to three radios simultaneously. Maybe…"
After looking at the first file you sent It does look that all you need is to add altitude offset to match the default terrain.
Unfortunately I cannot guide you through pix4d settings as I do not have experience with it and trial version does…"