Based on an assumption of fixed panels at the optimum azimuth angle 49° at 60°N.
Increased capture would lift the entire curve. I would think mount the panels on a 49° axle*, or put moveable shutters on either side of a fixed panel. Or spec better cells.
Here in the PNW, at about 45°, the sunny days of January are long gone and we're getting through the overcasts that we pay extra for to drive the Californians back home. I think it's called May because it may be nice and it may not.
*Patent US4476854 - Gas spring solar tracker - Google Patents
www.google.com/patents/US4476854
I see Stephen C. Baer's name on the [lapsed] patent, but in his books he gives credit to Day Chahroudi (the Cloud Gel guy).