The gap is a common well documented “feature”, even on OEM spoilers. Typically what happens is you have a slight rise at the extreme end of both edges – yours looks a bit more severe. And given the bowl shape formed by the trunk and the spoiler, debris/dirt/water will get trapped in there if the seal is not perfect, thereby weakening the bond over time. I’ve heard stories about OEM spoilers falling off and also driven a P90D loaner myself with flapping spoiler.

Also, it seems there’s only one double-sided tape in the middle that came with it? I thought the RPM ones usually came w/ two 1/4″ double sided tapes along both edges? Many ppl (including me) bought and applied generous amounts of 1/2″ tapes all over the backside, along w/ a good dosage of adhesive promoter.

During my installation I was overly wary about the risen edge that I pushed down the far edges down so hard and ended up having a paper thin gap about a quarter way down instead. doh! If I were to do it all over again I’d carefully push down the middle first and then push out on both sides.

The solution – assuming it’s on structurally tight – is to use a bit of silicon RTV sealant to seal the edge. Most ppl only seal the very end of the edge – I ended up sealing the entire top side. The silicon RTV solution seems to work well for me so far, aesthetically and practically.