No unfortunately, if you reverse engineer an image to make a home-brew install version preview map you won't have search function as said above. See the note in red here: [Only registered and activated users can see links. ]. That applies whatever known software you use to make the install version.

You can see and use the .img file directly in BC however provided it's Ms Flag is set to '0' not '1', but not to make a fully functioning 'short-cut' map image file with MapInstall or MapSource. In the absence of original PC Install mapping data, the only sensible workaround is to have multiple maps as separate img files on separate SD cards as you suggested yourself in the initial post. Garmin always makes their images under 4 gibibytes [i.e. under ~4.294967 gigabytes] in respect of the FAT32 files size limit of 4,294,967,295 bytes [4GiB minus 1 byte]. All common 4GB SD cards have less space than that so rarely a very large Topo may need an 8GB card.