Mines black to match the STI kit, not sure if adding this would do much for the overall look

When you install this is there anywhere for the flap to sit against on the spoiler? I want to do this myself but I want to make sure its not too tough to match it up to the spoiler after removing the cover from the tape.

Nope you just have to manually align it to the end of the spoiler

Is everyone buying form Japan Parts, or is there any other vendors of choice?

I bought this very same one. I want to fit mine today. What did you use to cut. Hacksaw blade? and did it discolor at all? If it does discolor when you cut it i think a little heat from a heatgun will bring the color back

does it matter what kind of alcohol you use to prep the surface? just regular old rubbing alcohol? wiped on? i was told to use adhesive promoter as well after that and then the 3m tape. (I'm not going to be screwing the flap in obviously)

What's the chord length to measure against. Windshield to tail or nose to tail?

From that video, will refrain from posting again.