I finally heard back from the customer support person, Mike, at Lance Campers regarding attaching PV panels to the roof. His advice was completely different than what I was told by the technicians at two Lance dealers in the state who each was doing something quite different when attaching solar panels to camper roofs.
For the Lance campers Mike recommends using hex head 3/4" #8 self-tapping screws into the metal channel that is located at the outer edges of the roof. At the front of the camper this is the boundary between the roof and the curved section of the cabover front and on the sides it is where the roof meets the walls.
For the other two sides out in the center of the roof he recommends using 3/8" well-nuts and using a silicon sealant to insure water does not travel down the bolt and through the well-nut.
The good thing about placing the panels over the leading edge of the roof is that the most secure connection is where there is the most wind force while driving down the road. I will be screwing down 2" angle aluminum along the front edge so the outer edge of the PV panel will be 2" back from the edge and hopefully less subject to air spilling off the front edge of the camper.
To be honest I got the same advice. I know there is only 1/8 lunan on the roof over foam. My 2 55" x 12" panels had a z bracket on from and back only. I used 3 large SS sheet metal screws at the front and 3 at the back of each panel totaling 6 per panel and Dicor Lap Sealant back from the outside edge as well as at the front. It has been thru many high speeds and winds.
I know from the last camper I was advised by Arizona Sun owner that just using Silicone II would glue it down and it did. When I removed it I had to make a Tuna wire or Piano wire (Guitar wire would work I bet) saw to cut thru the seam as no way you could peel it off the roof. I figured with large SS sheet metal screw and lap sealant under and over the brackets it would hold. Last camper had Aluminum sheet metal. Being this one had only Dicor TPR I used #14 1 in screws giving 3/4 or less to protrude into foam and not into inside ceiling.
I bet I could add a bracket of some type from the front cross bar easily. Lance told me to shoot the screw at an angle into the bar. I wasn't crazy about shooting at an angle. I was afraid to miss or trash the sealed roof joint.
2011 F350 Super Duty,SRW, 6.7 PowerStroke,Crew Cab,Lariet,4x4, 3.55 Locking Diff ,Short Box.Timbrens,Happy Jack's, Gator Guard bed liner, Penda bed mat.
2012 Lance 855S 9K Coleman A/C,Duel Batteries
I want an air gap under the panels to keep them running cooler and I want to be able to tilt them in the future for the winter months. By attaching first the 2" angle aluminum I can change the brackets for the solar panels without worrying about disturbing the roof attachment points or the weather sealing.
I know it is overkill but I will be using VHB tape as well for the angle aluminum as I plan to experiment with several panel tilt mechanisms I am in the process of designing. I want to be able to raise and lower the panels easily from the ground and not have to climb up on the roof to raise them and again to lower them.
The well-nuts were the critical piece of missing information.