even with installing many spoilers before on other cars including my old cars, i get scared every time i drill holes into the cars metal, its true that the spoiler will cover most of the mess up's but i hate knowing i messed up^ defintly tuned in for it installed man.
so i'll have to measure 1,2,3,4 times and make sure i mark it well before drilling..and because the middle piece usually mounts to the stock SI holes/tabs and because the trunk is fresh of holes i might just use some double sided tape..4 holes max!
about the homedepot lip its called Front King Garage Door Sealer
http://www.sears.com/shc/s/p_10153_12605_SPM5931367707P?sid=IDx20101019x00001a&ci_src=14110944&ci_sku=SPM6770414302
thats how it looks like, what i did was drilled the sealer to the bottom edge of the lip(not all the way) then used epoxy to seal it between the rubber piece and the lip..most people just use the screws but i didn't want any air getting between it and risk the chance of it coming off..i did about a foot and a half at a time and allowed the epoxy to dry (about 5 mins) before moving to the next section, as i moved along i'd epoxy and then tighten the screws more to really hold it on and i would also use some tape to hold the rubber sealer in place because it'll want to slightly pull away from the lip
i should've have done a DIY with it but was too excited and writing the DIY's take a lot of time