Mtngrrrl:
I have a 2007 Apex 8 with the electric roof option this lift allows the roof lift to have a greater capacity but does not affect the strength of the basic roof. We have an Outfitter installed roof rack and one Outfitter installed solar panel. This solar panel has been on the truck since 2007.
Our 2007 roof is plenty strong, I have walked on the roof, with it down and carried 200# on it with no problems.
On your question: I have reconfigured the solar panel that Outfitter installed and installed a second panel and will be installing a third panel when I get around to it and a new controller as well.
The second panel has been on the Outfitter for a little over a month and one trip of about 2000 miles at speeds up to 80 mph (this was to test the panel, I do not usually travel at this speed). The new panel has not moved.
I essentially used Outfitter's approach. Z clips from Windy Nation-ebay, they are commonly available. The Z clips are set in Dicor and I use a structural large round head screw about 1 1/2 inches long (These are not giant screws they have a 1/2 inch head and maybe a #10 shank but with slightly larger flight, I get them at Home Depot in a clear box of maybe 50 to 100 for $10, where they keep the various metal plates for structural lumber) going through the Z clip and Dicor, they do not penetrate to the inside of my roof. Top off with a generous amount of Dicor. Use wire cable clamps to hold down any wires more than say 18 inches long and maybe less, more Dicor.
The front edge of the solar panels is about an inch back from the face of the Outfitter. In this area the airflow is pretty disturbed and does not have the force necessary to rip off a solar panel.
Check the thickness of your roof to see what length screw you need.
Plan your system to include upgrades now so you know where you are going to put things and how much controller and battery you will need.
Good luck!
Rick