My memory usage is a bit different, in that I NEVER put anything on the Internal memory unless I am going to use it on the gig.
Everything I am just testing out goes to external, and gets transfered when it is gig ready. This way, I don't fill the Internal HD with unused stuff. To date, I still have plenty of room for whatever I need. Having no audio capability can make 30MB or so (what is left over from 50MB after the OS and ROM styles and UPG's are put in it) go a LONG way...
Mind you, I remember the E50 as having a much smaller HD. Perhaps having EVERYTHING on external might be the easier way for E50/60? That way, a simply copy to another card will give you a backup... that's why I don't like using external... get it stolen and there goes the gig. But use it 100%, I suppose having a spare hidden somewhere might be good...
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An arranger is just a tool. What matters is what you build with it..!