Hi Andyblue,
I am assuming you have the same model unit?
Well I have managed to enable both maps by Selecting the area on Shonky maps, then pressing the uploading to device tab. It will then tell you whether or not it has successfully loaded to the unit.
Once you start the GPS, go to the location where you have loaded the map, to ensure it is there.
By pressing the menu button, go to setup map. You then select down to the Map Information tab, and select it. You should now see the Basemap, Birdseye Satellite, and whatever other maps are loaded onto the unit, just enter into them individually and you will be given the option to either enable it, or disable it and there you go!
I have noticed that having the custom Game Council Map & Shonky(Mapsource) Area map enabled at the same time, conflicts at certain Zooming points and one will supercede the other.
Sorry it took so long to reply, we just got back from the hunt this morning, I had a great time. Unfortunatly there was nothing to be seen, no signs or game in this particular State Forest, but just getting out there was great. The GPS worked a treat, and I am glad I picked it up, it could get messy heading out into an unknown area with out one these devices.
Cheers,
Jack