Hood scoop cracking prevention ?

I think i used about 20 stainless screws. There was no such thing as panel bond when i did mine. ALL i used was the screws, i didnt try to bond or blend the scoop on, it was obvious it wasnt stock, and i heard that a bondo or fiberglass blend would crack anyway.
I think your technique has far more chance of longterm success than mine. I think if i were doing mine again, i would get the kind of sixpack scoop with the bolt on provision, rather than the flange type.
With the flange type, i would probably open the hole in the hood up to the size of the scoop, and use some fiberglass mat on the inside, wrapped and bonded to the bottom side of the hood.