In fact it's exactely what I want to do (to be able to have the Countries or states of my choice ) because even if my Goldwing is able to read cards bigger than 2GB, it won't read the .Img file larger than 2GB.
I don't understant all that is written on this post but it looks as if the solution is there.

For now, I have to use two CF cards. One with the 2019 Canada maps (432 000 Ko) and swith it to an old North America under 2GB when I need to go to the States.