i had 3m tape on a acs roof spoiler. must be the extreme weather here, it came off within 3 months

 

3M double sided tape should be suffice

 

I used a silicone adhesive on my ACS replica spoiler and that sucker is solid. It was a mess and I think I used too much adhesive but it's on there for good. Cleaning the excess adhesive that leaks out the sides is a PITA and have only cleaned a part of it so far. Also, I don't recommend putting the spoiler on at night outside. I woke up to find that I put it on slightly crooked and it's bugging the crap out of me.

Good luck to you! And that ebay spoiler should be fine. The only thing is paint fading or chipping/cracking on it but I doubt that will be a problem, at least for a while.

 

it wont fall apart within 2 years just cause its a rep.. mine was off of ebay, came primed and all i used was 3m.. once that tape is on the spoiler and it touches the car.. it isnt going anywhere.. when its hot out i can squish it a tiny bit, but by no means can i MOVE it..lol.. your problem with a rep trunk spoiler is going to be fitment.. i have a slight warp on my roof one, but its small and unnoticable, especially with the tape sucking it down..

 

+1 for beta links. Double side tape won't last, I have my RD roof and trunk using 3m, it's on the verge of coming off and I only had them about a year. Once some particles/dust get's inside and touches the sticky part, it gets worst over time and you will loose all the stickiness eventually.

 

3M is good enough. Just make sure you install it in a warm place. The first two times I installed it was in the winter time and it came loose. Third time, I installed in Spring and never came loose again.Heat the surface with a blow dryer and slap it on. I did this for my RDSport roof spoiler. Then tape the hell out of it to hold it in place.