I'd be curious to hear from anyone who has glued new luan panels. I thought that it was just the vinyl that was unglued but when I started tearing that down, about 2/3 of the luan also came down with it! I've since repaired the Filon roof leaks (Dicor lap sealant and Dicor Fiberglass RV Roof coating) and am getting ready to tackle the ceiling. I've got all the foam exposed sanded and prepped. It was suggested to me to use PL Premium but being a polyurethane, it may not provide good adhesion to the foam ceiling. I'm now considering the Green contact cement or Liquid Nails LN-903. The press-tite green contact cement is water based and compatible with foam. It's easily spreadable. The LN-903 is very weather, humidity and temperature stable, but comes in a tube and will be much more difficult to spread evenly. Any other ideas?