Best thing to do is climb up there and take measurements. When I did mine I got the measurements from the panels to determine where they would fit.
You want to make sure shadows from a/c units vents,and whatever other equipment is on the roof don't fall on the panel placement and reduce their efficiency.
2005 Safari Cheetah 40PBT C7 Cat, Progressive Ind. EMS, Blue OX Tru Center, Lithium Batteries, 800 Watts solar. 2014 Jeep Wrangler