I hear ya all on that theory and gave it some thought...I took my spoiler off to tint the third brake light and noticed the original gaskets were no longer conformed..I was concerned about snow/ice/salt mixture in winter being able to get under it and freezing..
Since getting a new gasket for a SPO would have been nearly impossible I just banged the head about similar gasket material..The best choice for the buck was the black rubber, sticky foam tool-box drawer liner..actually it seemed to be better gasket like than the original gasket... a huge ass roll only cost $5
I traced the spots out,held them in place with rtv and let sit over night. Before I put it back on I drew around the bolt holes with rtv and then placed the spoiler.
Nice and tight with just enough cushion.