I'm sure 3.08 rear end gears aren't helping. We do seem to migrate in and around mountains. So passes and windy roads.

If you were heading east it could have been the winds, we averaged only 5.75 from Oklahoma thru Kansas and partway thru Missouri and we had heavy cross and head winds all three of our travel days. I think it was the worst I have seen in 8 years with our HDT.

So, just about home.  Traveled about 1000 miles. Average mpg.... 4.7 Ouch! Maybe detuning this baby to 425hp?

My wife and I are in our 70's. Our experience is with a 1996 25 ft class C Jayco with a bed over cab (my spot) and a rear queen bed for my wife. (We have no animals or kids.) It is pure joy to travel in and to live in. It would be a challenge to fulltime in it as a boondocker, lacking the large gray and black tanks as well as the freshwater tank. It does great in a 5 week trip. You will have no problem with storage. It's built on a E-350 Ford chassis. Everything was trouble-free across our two maiden voyages. We got into this for $10K. 

Thanks for the tip. I have not posted there but I will.