Unfortunately, my mind is already working out an improvement. I don't have the time or the willingness to undo all my recent work now, but it's a project to try next year, or on someone else's house. The thermal capture from the naked panels in the sunshine of July was impressive, and it would be good to be able to open them up to the sun in the day and close them at teatime. I thought about it at the time, but decided that panels opening with a bottom hinge would be too dangerous in wind conditions, and make it difficult to do regular maintenance.
Talking about it with Mrs NC at teatime, I thought that I could construct a big Sliding Front model, that would be closed most of the time, but the user can reach up with a boat-hook and slide it down on good sunny days. I will make an ArchiCAD model of this quite soon.