Update: I took the Stainless Steel Z channels that came with the panel and used my high speed cut off saw and cut them in to 2-1/2" sections, I then cut the top off of them (one part of the Z) Now I have eight "L" brackets to use, I will measure the width and mount them to the rafters at 18" on center and attach my panels.
Thanks for all the help and suggestions, This is a wonderful forum with many useful hints and suggestions!
Bob
One end of the panel will not be on rafters, because your panel is 59" and closest rafters are 54" on centers. You can't put L-brackets lengthwise without some wedge, so you have to put them crosswise, oriented along the rafters.