Charles - I think your reply was caught in the quote section. The splitter was the first issue in the four 8 hours I've done. Pretty amazing.
I run on shaved Toyo RA-1s. My car seems to like them and they can last the whole eight hours. Not changing tires is a time saver that comes close the cancelling any advantage you would get running a faster tire. Our total time in the pits is usually quite low. Not counting the unplanned splitter stops, we would have done it in 6:19 this year. Speed showed a graphic at the 8 hour mark of their Sebring coverage showing the best pit time was the Andrettti-Green team, which was in the 9 minute range. It's not apples to apples but we're doing okay.