We've been going up there every summer for the last 10 yrs. We stay at Narrows Too. I had looked at Bar Harbor CG, but the lack of reservations was a deal breaker. I don't want to drive 1700 miles and find I don't have a place to stay. People say that isn't a problem as there are always open spots, but I didn't want to chance it.
I stopped at Bass harbor CG, which is on Mt Desert Island and they have a half dozen or so sites that will accomodate a big rig... but, they are under pine trees and I didn't want the sap on my roof.