I used a stud finder and marked the studs with chalk. Then made a cardboard template of my panels + mounting brackets. I moved the cardboard around (used chalk again to mark the boundaries) to try to optimize the panel/roof area.
I learned Aligning them with the roof studs and optimizing layout is not compatible.
Once I was satisfied I laid the panels with the feet attached where I wanted them. Marked the brackets position lifted the panels and put down Eternabond. Then laid the panels back down.. Then put a generous amount of Alpha sealant under each bracket. Then pilot drilled the holes for the screws (2 in each bracket). Filled the holes with Alpha sealant. Then put in 3/4" × #14 SS screws.
I made my own tilt brackets. If I was doing it again I would buy the Renogy tilt brackets.
Watch the Keystone Montana factory tour video to get an idea how they put the roof together.
https://youtu.be/cV0OZv0bCgc