I agree with what seems to be the general consensus: Dropping one band and lengthening the set of the others is OK *only* if you don't drop a band that we'd be upset about losing.
Of course, unless you're psychic, that's kinda hard to know before it's done. *:^)
Why not keep it at 5 bands/day, and simply lengthen the festival as a whole by one hour each day, and add that time to each band's set? That would add nearly 15 minutes PER band (which gives them an extra 1-3 songs, depending on the band), yet only increase the duration of each day by an hour or so.
I know there are issues with venue booking, paying staff, etc, that would need to be considered to lengthen each day, but *I'd* be willing to pay another $5 or so for my ticket to cover the costs of lengthening the show this way.
Just a thought...
Craig
P.S. Of course, I'll be there (3rd in a row!) regardless of how you handle this! *:^)