TEK figures were close since I came up with a focal distance of 52.71 inches. With the existing pre-drilled holes (5 of them on each panel), I could only get out to 51.5 inches. So, my options are to drill more mounting holes or get longer support rods. I just happen to still have my old Paraclipse rods that are longer than the TEK rods. I'll give them a try. Anyway, calculating the focal distance gave me the opportunity to do the string test also. Surprise, surprise, surprise! The string test is good.