Rich, here's a different perspective on this. I trashed my speedometer thing a few years ago. Too complicated for me to make it stop blinking 12:00. Instead I use the stop watch function on my watch and measured the time it takes to get from point A to point B. I explored different routes and over a few years developed a mental map based on the time it takes riding to get to one place to another in my area. And usually the straightest/shortest route is not the quickest. For example the logical/straightest/shortest indicated by a road map from my apartment to downtown takes about 1:45 minutes. The route I now take (convoluted as all hell by road map standards) takes about 1:15. I saved a half hour I think mostly by cutting my route from 20 stop lights down to 4. Hills aren't so much of a problem provided you get the payoff of nice long unobstructed flat ride at the end of the down hill side. Avoid routes where the down hill ride ends right at a stop sign or stoplight. Because of those my going route and return routes are rarely the same.

Anyways, you indicated that you had about a 20 mile ride. There is potential for alot of different routes in that distance. Maybe a longer one will prove to be the quicker.