Tom,
As I have said the F1 teams are in a continous development program on their engine air inlet scoops and they can and probably do anything you might even consider that could affect the scoop efficiency.
As far as having a "vent" hole in the scoop I am against this approach for two reasons. 1. You are probably bleeding pressure (air) out of the inlet which is exactly why you went to all the work to build the thing in the first place. 2. A vent hole promptes air flow thru the scoop which will cause an increase on drag, now that would need to be balanced against the drag that could happen if you made the scoop inlet to large for the engine requirement and you would then have air, and probably turbulant air, bleeding out of the front of the scoop. Probably a good place for some testing at your "Air Flow facility".
I do think that you need some sort of guide vanes on the inside of the scoop to get the air pointed into the carb. Another thought is providing some sort of "dampening" material inside the scoop, like a good high flow air filter, to help reduce and any interior pressure pulsations. I have always wanted to try lining the large volume section of the scoop with some very porus foam, like fuel cell foam, to provide internal dampening. Another thing to test at your "Air Flow facility". Build a scoop with your best thoughts and then put a Magnallic pressure gage connected to the inside and see if you get good pressure recovery, make changes and see if you can get it better. For us guys without unlimited budgets the old "cut and try" method is probably our only way.
Good luck, Rex