Thanks! And I've seen Dave's tests. Since I don't need a fixed angle, do need to maximize production (due to a limited sun horizon), and only have 10 panels, the best option is adjusting angle during winter. The N-S orientation is a really poor performer. (Notice that his test is 30-degree tilt vs N-S; 60-degree tilt will provide 20-25% more power than 30-degree at my latitude, without even considering bifacials w/snow. The only thing that would produce more is an active tracker, but I've got other things to do, and a December deadline...)