Weird, two Bolands on the same thread!
Alex you can do it with tiles or GEOTIFF both from global mapper. With GEOIFF you must select custom imagery under source in the upper right corner drop down. Then hit CNTL F to get the menu to upload your custom imagery.
I don’t have mission planner in front of me and can’t remember the name of each tile. I can provide more specify assurance when I get to mission planner, which may not be for another 24 hrs.
Once you get it working, it’s awesome.
Dave