Mine came with zip ties for the transfer method. It worked with no problems. As stated, put zip through mounting hole on spoiler, put rolled tape on end of zip tie, lay spoiler on trunk, remove spoiler and zip ties stay. I also taped off the area, traced the spoiler, and then measured from spoiler edge to installation holes to make sure I was really close just as a double check. My spoiler came from spoilersolutions.com. Its been on for a couple years now with no leaks. Pics at bottom of link,
DIY: Roadster Spoiler Install