I've been staring at my New Hampshire Atlas and Gazetteer (available for all the states around here at REI in Reading) for some good roads.
I'm thinking of meeting at Littleton Common (we used that meeting point for our first DML ride last year, seems central to a lot of people), and heading out 119.
The Gazetteer is detailed enough to give you a sense of the curves, though it has no elevation lines and so you have to guess at the verticals based on peaks near the roads.
Anyway, I'm planning to scout some roads in the Milford, NH area and NW of that. I mapped out one route through Keene and meandering back on the windiest secondaries I could find. It came out to almost 200 mi, a little long for a back-by-lunch ride. I think I just have to explore. there should be some good tertiary roads in there too with much lower population density than over closer to the coast.
Do we have anyone on this list that lives in the Manchester area and knows the roads west of there?
I'm out of town for the weekend so I won't get to do any scouting until we get into September.
In general (except for the occasional marathon) I like your parameters: 7-12 with a social hour included.