This guy got it going. ;-)
GE has an "aperture" size that doesn't appear to be consistent between PCs. GE expects the images to be tiled with no tile larger than the aperture. On my PC, that is 3600x3600. That is probably why you could load the Radio Mobile output to GE.
Incidentally, there are programs designed to take a PNG and tile it, but I never got them to work. But it has been a while since I tried them.