The tape is not mendatory in the front. It just helps keeping the flap sitting flush with the fender.
The way you have installed the tape is definitely going to be an issue. You should have cut a smaller piece and put it where there is no cutout. I'll specify that in the instructions from now...
That's the stuff right there, althought I believe properly cleaning the surfaces with isopropylic alchol and heating the tape, bumper and fender liner prior to installing the tape would work just fine.That 3M adhesion promoter is no joke and might ruin your paint trying to remove the double...