I couldn't get this method to work so I removed the whole spoiler and cleaned everything up and removed the old tape. My buddy owns a wrap shop I'm gonna swing by there and have them assist me with the remount.Did you just stick some 3M tape in there....heat gun it and push/hold the ends down and it’s sufficiently holding?
I tried to measure equal distance left and right from the trunk lid but that resulted in one edge not sticking well. It seems better to use the natrual shape of the spoiler to set the alignment and not get hung up on the measuring to get it even. That's my takeaway anyway