Hi Dave,
My grill doesn't sit behind the opening, but inside it. If you look at the photo below, you can see the shadows of the bottom of the grill inside the opening. Check out
post 118 for detail.
I have used pipe for the 4 horizontal slats of the grill, then fixed 2 bolts from the inside to either end of the 2 centre pipes. The ends of the pipes were filled with JB Weld, then tapped for the bolts to lock in to.
Initially I tried to fix the grill to the car, not the bonnet. It worked, as long as I never needed to open the bonnet again
The front spoiler on the bonnet caught on the grill when I raised the bonnet. That's when I decide on fixing it to the bonnet (as shown above).
Your Kobra does look awesome. I love the 'purist' look. Stark and minimalistic ... very nice. Fixing the grill behind the opening works well. I am not sure that my approach above is any more professional. At the end of the day, passers by will not see the silaflex (awesome stuff by the way).
I will take some photos of the modded runners and post later. I haven't even thought about the seat belt sensor yet - but will.
Cheers
Chris.