I drilled the mounting holes for the two rear grab bars. I then followed Bob Lussow's recommendation and fabricated a piano wire with an L bend to insert through each hole and between the two layer of cabin top fiberglass. I chucked the wire in my drill and used it to clean out the honeycomb around each hole. I vacuumed as best I could the loose material broken up by the wire. I then made a runny mix of flow and injected it into the voids. I followed by injecting more straight epoxy continually working the mix to get rid of any air voids.