Thanks for the reply. Yes, I worded things incorrectly. 4GB - 1byte is the FAT32 limit for a file, aka single .img. You can have multiple .img's on the device, however all maps inside the imgs must be < 4,000 total maps. I have noticed as the map count grows, it takes longer for the device to start up. So far, loading up nearly 4K maps in separate .img files on the device (these are mostly Garmin TOPOs), I'm at about 8.6GB. Given that, I suspect for the person trying to cram in the most amount of map tiles on an SDHC and also add some raster images, 16GB card should be sufficient. For the personal sticking with the single standard 4GB .img, which I suspect would have generally much less map tiles (and faster load time), 8GB SDHC is probably a good choice.

I would still like to hear more about how people efficiently manage their maps.

Also, hoping someone works on an open source Garmin IMG creation tool/library like cgpsmapper and/or tkmap. It would be very useful so both Open Street Map and NOAA ENC/S-92 data could be automatically converted vs a manual process. Even better, this could be done on Unix.

Thanks again