I did it with a friend in 2001. We won the helicopter trophy but actually to put it in perspective we were the only helicopter entry. We went round about 38 old WW2 US 8th Air Force bases in a day starting about 0800 and finishing at 1700. The hardest part was actually the preparation which involved getting landing permission at 38 sites which were mostly farmers fields and involved months of correspondence, plus the documentation afterwards which took me weeks to do. Great fun though and a we saw a lot of very interesting places.