Nicklas, If your hood is original, keep it, even rework it if needed, maybe post a pic of the amount of bow you have so we can look to see if the support structure needs to be broken loose from the underside.
Yes the originals tend to not be a perfect match to the fender contour, largely because resin shrinks as it cures, so the curvature of the hood will close up a little as the resin cures. The support structure helps with this a bit but does not cure it completely. Personally I prefer the look of an AAR with a little bow in the center, its simply a part of these cars.