1) Order the one for your particular vehicle if you can otherwise the curvature of the side rails may not be correct which will dent the metal once secured.2) Look/feel under the headliner if you can prior to drilling into the roof, you may hit a beam which will be troublesome running a screw through multiple pieces of metal. You can also cut the side rails if necessary.3) Use non-corrosive silicone (does not smell like vinegar which will eventually eat away at the paint and rust) to seal up the holes that you drill into the roof. End caps doesn't appear to make a tight seal.4) Screws are stainless which are typically soft. Be careful not to overnighten! I actually used a rivnut/blind nut tool instead of just screws (About 25 bucks here on Amazon).

Above Deck Rigid Foam Insulation for Existing Roofs