Fiberglass hood mods... crazy?
I ran a fiberglass hood on my 68 Dart back in the 80's and the way the Dart front end is designed, they do trap a lot of air. a teacher I had in high school had a 68 Dart drag car also and he had the same issue.
I played around with different ways to mount the hood and I found that if you use longer hood pins, you can make up a light spring that goes between the top of the hood and the pin. This allows the hood to rise a little when the air builds up in the rear of the engine compartment but keeps the hood tight when not racing. Just make sure your pins have a slight angle towards the front of the car or the hood will bind when it tries to rise up.
The piano hinge won't work unless you elongate the holes for the pins. when the hood tries to fold the pins will keep it from folding because when you fold something, it gets shorter but the pins will be stationary.