Tim,
My route sounds like yours. Mostly rural highway, with the rest city/suburbs.
I got 63 MPG this morning.
The highway has a 55MPH limit, but I go 45. It's 2 lanes, so traffic passes me all the time.
NEVER USE CRUISE CONTROL. RPMs rev too high on even the slightest of inclines. I actually slow down on any incline and let gravity help on the way down.
Keeping the IMPG gauge between 50 and 100 has helped out immesely too. It leaves plenty of charge for when it's needed, while achieving a 60-70 MPG while cruising.
I have a HCH2, which has more charge capacity. So trying this might not have the same impact on a HCH1.