Jim, If you're using the SkyGuard, then the iFly software is pulling the GPS data from the SkyGuard and not internally from the Nexus 7. (You could possibly improve your GPS reception by relocating the SkyGuard GPS puck antenna for a better view of the sky.)
Jorge, I have used a yoke-mounted Nexus 7 (2013) in my Cherokee, and had good results with the internal GPS. (I fly primarily in SE/E Texas.)
I have seen, though, the airplane on the moving map stop updating on rare occasions. Exiting and restarting the app always restored the moving map to normal operation. (Not sure what indications you were looking at to conclude a loss of GPS...could you be more specific?)