Didn't Dennis become a 5 and even make landfall as 4 or strong 3 but do little damage because, in part, it fell apart quickly? It was also moving forward at a nice clip.
A most excellent site/model about impact on oil production, (offshore rigs) updated with NHC updates.
US Gulf of Mexico Oil and Gas Production Impact Estimate for AAL182005
http://hurricane.methaz.org/hurapak/AAL182005_gomex_oil.html