You'll find that skin panle seams almost never leak, as the whole
overlap between the two skins is filled with a wide band of sealant.
Almost always it will be "extra holes" in the field of the skin panels
as Daisy has noted: A/C mount holes, awning supports and rails,
antennas, lights, owner "add-ons", screws. Many window styles will leak
too, and they can be found with the two person water hose method.
Best of luck,
RJ