The setup.exe file from Navigasi gives you the choice of building a full default image file gmapsupp.img directly onto your computer hard drive for transfer to your unit, or installing a MapSource [PC] version from which you can create a partial or full map to send to your GPS. Regardless of which method you use, the resultant map image will have an MS Flag of 1, so it cannot be viewed directly in BC without changing it to 0. But of course if you use the installed version, that can be viewed in BC or MS anyway. So i guess you've used GMapTool just to change the flag on the image file.
The crowding is probably because you had checked 'Detail Level' previously when you were really only viewing the Global map not the actual CN. Uncheck it and see if the detail is less cluttered but even with Detail Level ticked the Garmin CN map seems ok to me:
What you see in MS/BC is not necessarily what will show on the GPS screen anyway. In my 2610 under Menu>Map Setup>Map Detail there is a choice of 'Most, More, Normal, Less, Least'. I leave mine on Normal usually.
To place a second map as gmapoem.img in the 2720 just use exactly the same procedure in Post #3 as for gmapprom.img with the name changed accordingly and rgn=50 [should work, i haven't tried it and it may not be selectable/de-selectable anyway], or much better method is to use MapInstall with a PC version to send what you want to the unit memory named as gmapsupp.img anyway.
The 2720 has 750MB of on board memory available for maps etc to be loaded [as far as i can recall]. There is quite a good review by Joe Mehaffey written at the time of it's release. The page link is below which will give you far more info than the Garmin spec page also below:
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