I read in this forum sometimes ago that someone suggested using anchor screw to avoid going through the ceiling. Anchor/Screws: Steel Threaded Inserts - The Insert Company (UK) Ltd
an UK company
Steel Threaded Inserts for Solar panel anchor
High quality zinc plated steel and stainless steel threaded inserts.
Zinc plated steel screw anchors / hollow wall anchors, for use in thin sectioned materials; sheet metal, fiberglass, plastics, composites etc. where one surface is inaccessible.
The head and collapsible legs form a load bearing surface on both sides of the material.
Will this anchor screw work to secure the solar panel? Casita uses a lot of rivets through the fiberglass without any problem.