mounting my solar panels

I have ordered some solar panels to put on my TT. I bought the 200 watt kit from Renogy. I doubt that I will be able to determine where the structural members are, so there is the very real possibility that if I just use screws they will only be into the plywood decking. In any other applications, I would trust this, but not for going down the highway at 60mph. Therefore, I am thinking of using expanding well nuts. Good plan? Or does the collective here feel that the screws should be enough?
Also, what is best sealant to insure no leaks? No clue what the roof surface is. TT is a Gulfstream Conquest.
Bil