This photo shows why it was not feasible to mark the light locations based on measuring the ceiling panels when they weren't installed. The don't line up:
I temporarily installed each panel, then used a carpenter's square aligned with the roof framing to make my marks for each light location. This was used to determine the distance from the wall.
Then I used a metal ruler to measure the distance between each light, which is 32".
Then I drew a line and marked the center of the light, and 1" out from the center for the mounting holes.
The ceiling project has been really time consuming. One of the panels had a plethora of lights in it, which was the second panel from the back, so I had to have an assistant hold the panel in place, while I connected the wires. We did that on Monday.
Today's project has been finish the ceiling and put away all my tools and wiring supplies, then clean up inside. There was a horrendous mess on the floor, even though I'd already vacuumed the floor when I worked on it about a week and a half ago.
I made a list minute decision this morning to attend a Dual Sport motorcycle event, so that was why I focused my efforts on getting the inside cleaned up today.
Here's a photo with my DR-Z400 ready to go tomorrow.... I loaded it up about 9pm tonight