Ok I think is see whats happening. In the G disk you named Derek which is the SD card you formatted to fat 32, create a folder and name it Garmin (as I spelled it) copy your .img file to that folder, power cycle gps and CA-Central... should be their. I'm not a home now so I'd need to look at one of my gps's but I think there is a setting for internal/external maps. Give this a try, I'll also look later at the settings on my unit(s) and post back.
It is considered a better practice to put your maps on the sd card as I've seen stories here and elsewhere about people borking, mucking and bricking their units when they accidentally delete stuff they shouldn't have in the internal memory
It is considered a better practice to put your maps on the sd card as I've seen stories here and elsewhere about people borking, mucking and bricking their units when they accidentally delete stuff they shouldn't have in the internal memory