This is what IFMAR has in its tech book
5.15 Only the following air holes and sizes are permitted in the bodyshells:
One (1) cooling hole may be cut in the front windscreen only (not intruding on either
the roof or bonnet) with a maximum dimension in any direction of 60.00mm.
15.00mm maximum diameter hole in the roof for glow plug access.
Both front side windows and the rear window can be removed for ventilation, except
for the side rear windows, which must remain intact.
Re-fuelling hole maximum 50.00mm diameter.
Small holes can be made for the exhaust pipe, transponder and radio antenna.
No other holes are permitted.
5.16 Roll-bars (roll-over bars) must be kept under the body.
5.17 No part of the car, except the muffler outlet, may protrude outside the bodyshell
So the second option of only one hole divided between the windshield and the roof must've been enforced during the worlds in Brisbane, but hasn't been yet included in the rule book.
AFM