Unfortunately, Renogy's 150 still will not span the tracks. So I will buy some Z or L aluminum at my local Metals Supermarket and install the 100W panel on the aluminum across the Yakima tracks. After reading more, it seems like 100W won't quite cut it between shade, angle, latitude, etc. So another panel is in my future.
Here's the question: Does the other panel have to be 100W? Can it be more or less? And, what about getting a fold-able panel for the second and plugging it in to the rear solar panel plug? If the fold-able gets full sun and the roof panel is shaded will it be a problem?
As an aside:
I found the wires needed in the battery compartment that come down from the solar plugs on roof and rear of camper, I hooked up a battery to the roof plug and identified the + and - wires (they were red+ and black -) and the shielded end of the plug is the +.