These flat plate panels in the photo are used by my Sister in Law on the hillside behind her house, facing due south. They do a splendid job of providing all their hot water through the summer.
Another thing that has bothered me... the roof ridge is North-South, meaning that we dont have any ideal roof angles. The south facing Garage roof is too small and is over shaded. So if we wanted ideal solar capture, we should have one on the west and one on the east face, so that capture takes place through the sunny day. However, this complicates the plumbing and I am somewhat anxious to keep all the 'gubbins' on one side (the East), for easy maintenance.
I am told that Flat plate work better on an East or West facing roof than Vacuum... lets hope so. Two things, they are cheaper than an array of Vacuum tubes and less prone to wind damage.