I have a fiberglass '69 Cougar Eliminator scoop on mine. What I've gleaned:
1) I had to reinforce the scoop underneath with a steel bar encased in fiberglass, as at speed the scoop would "balloon", and it cracked the paint at the front of the scoop
. This could also be because I have a crap ton of air coming in through 2 grills in front, and no where for it to go. (See point #3, below.)
2) My air cleaner sits about 3/4" above the hood level, and I have about 1" clearance around the edge. If you cut the hole, be prepared to take a bazillion measurements. It's a royal PITA.
3) If I had my druthers, I would have put it on backwards, like a cowl scoop. Lesson learned lol.
4) I have a foam plug I put in it when it rains. I'm not a fan of wet air cleaners.
5) FWIW, my scoop does help to cool carb air. I can tell the torque difference when I have to plug it up lol.
6) Put some sort of anti-friction foam or tape in between the scoop and your hood (when/if you paint the hood). Foam also keeps water out.
7) Pop the hood to let it cool to prevent damage to the scoop. And yes - lots of heat escapes from that hole in your hood, but it butts up against the scoop on its way out and will warp it.