There is a ring of steel welded in that goes thru the hood from bottom of the reinforcement ribs to about 1” above the hood itself and then body filler transition to the hood surface. Yes that filler cracks at that seam and no you can’t see it under the scoop unless you look for it. Hard to see in this picture but I can’t find the ones I thought I had so will have to take a couple new ones. Like I said, I didn’t do original install but cleaned up the install and repainted it all.
Jetting issues I assume you are talking carb and I don’t have any issues with my tune after getting it all dialed (Edelbrock 750 on a 340 with 284/484 cam). I have driven this car on 90 degree summer days and 30 degree winter days on the same carb tune. I am a hair rich for summer and about dead on to hair lean in winter but there’s no jet change for that so it’s just fine lol. Only issue would be getting caught in a rainstorm with fully functioning scoop and no block off methods.