Read link for comment on the subject of potential 747-8 WING flutter problem with the tail tank more than 15% full. The quick fix apparently is to inhibit the fuel system from carrying any fuel in the tail which obviously results in a reduction of range. The permanent fix has not been announced:
Business & Technology | Boeing blocked from carrying fuel in 747-8 tail until problem fixed | Seattle Times Newspaper
Edited to correct previous and clarify a wing flutter problem rather than a tail flutter problem.