Holes may be cut in the bonnet to allow the protrusion of an air cleaner or carburettor above the bonnet line providing the protrusions remain underneath the bonnet scoop. In these circumstances, the bonnet scoop or raised bonnet section must be manufactured from mild steel of equivalent gauge to that of the original bonnet; and
If any bonnet reinforcing braces are cut or modified, the design of the modified bonnet must be of equal strength to the original bonnet and any sharp edges created must be suitably treated.
Actually my GV bonnet weights 7.9 kg which is the same as the OEM. The vent in the GV bonnet could not be cut into the OEM as reinforcing braces would have to be cut. Also the vent would allow something like this to be fabricated (from http://www.miataturbo.net/race-prep-75/serious-cooling-ducts-hood-vents-think-gt40-now-pics-57909/#post728899) and keep the engine bay cooler as well as have more control over the air going into the car. I have a lot more space now that the air con and power steering have been removed.

Bruce I may take your idea and see if an OEM bonnet can have a GV like vent added that complies with the law and takes advantage of the ducting that I'm thinking of making.