I tried to use two gps-receiver as incoming sources and use one virtual comport as outgoing. I can confirm position-hopping, because both receivers never give out exactly the same position. In addition to that, if just one receiver has a fix, a gps-software switches between fix and no fix, every second.
Howardn, to use gpsgate with two receivers and your navigation software, you can use two different instances (Advanced-tab) in gpsgate. Assign two different virtual comports to every instance, and your navigation-software can decide by priority, which comport it uses.