Update on the 49,824 KB basemap file.
I went ahead and deleted the old 6,056 kb gmapbmap.img (backed up), and installed the new one (49,824 KB).
Unlike my previous failure in the diagnostics mode, this new basemap file passed.
I will keep it on there for now unless it slows down my device as catymag suggested.
I may be wrong but I don't think it will slow down since the primary map (2011.40) is what the device will use.