What is the use of a refresh rate of 5 - 20 Hz, considering that the satellite signals only arrive once per second?

You could connect a laptop with your usb gps gadget and run gpsd. GPSapp already has the code to connect to gpsd, it just isn't enabled, but is shouldn't need more than removing an #ifndef __arm__ and changing the ip-address to that of the laptop.

It will give you the large screen as well. But with this solution you can just as well run gpsdrive or something similar on the laptop and take the empeg out of the loop.