Efficiency: If I were going to ride PBP on a derailleur bike, I'd put on a new set of ceramic jockey wheels for my last few weeks before France. As pointed out above, jockey wheels do have some slight friction.
One study of DNF I saw said that one of the best predictors of success was having one pannier. One of the best predictors of a DNF was being over 70. So it seems that being young and having a wide variety of clothing available is very helpful. One of those 3 oz. bivvy bags might be nice. There are better options than panniers available now.
With all the complaints about hand fatigue one hears, I wonder about the reliability of electronic shifting vs. cables.
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Results matter