Vu - I'd think twice before you invest any time or effort on that project as I was considering buying one of those scoops last year but went a different route.
Maybe your set-up is different but when I looked underneath my car I saw that the scoop would be pushing the majority of the air over the top of the cooler.
Instead, I bought a piece of sheet metal and formed a tray which I mounted on the bottom of the cooler to the front valence which prevented the air from going under the cooler. I then used some of the plumbers foam (ie., the stuff that gets wrapped around the pipes) to block off the top and sides of the cooler so now the air couldn't escape there either.
End result is that the air has nowhere to go except through the length of the cooler as all of this has in effect created a tunnel. Although I did consider it, I didn't even cut out any of the notch that exists between the bumper and valence.
The impact of these changes were immediately noticeable and now with the new engine thermostat my temps never went above 210 at either of the track events this year.
BTW, I choose to remount the horns although I could have gotten away with just bending them out of the way but I figured why leave them in there to divert the air flow. Instead I bought a $7 horn from Advance Auto and wired it in and now that serves as a support for the front end of my tray
Good luck and let us know how it turns out ...