Thanks groar.
I think the alternator disable has a large hand in it. I admit I did more focused driving vs my last tank (62 mpg). I had my
mpguino working for most of the tank, and that helped. However, disabling/re-enabling the alternator is
very noticeable. I'd say its more noticeable than turning the AC on and off. You can feel a difference in acceleration as well. On the trip to get the Prius, I drove to the dealer with the alternator on. When I'd shift to neutral for my glide, I noticed my rpms dropped like a brick. On the way home I disabled the alternator and the rpms dropped much slower.
I'd highly recommend this mod for anyone who can get their hands on a decent deep cycle battery.