There is quite a bit of light produced by the moon.
Your best bet for cooling is creating a barrier somehow but yet still allowing air to flow.
You should just take a piece of duct and zip your zipper down to it snug, then maybe take a black piece of plastic and drape it over the joint. The key here is to have the duct long enough with enough bends that the light projection is shortened and there should be little to none through.
Take a booster like this and put it on a 6 inch duct that is about 3 foot long shape it like an S.
On the subject of light leak. Plants take more than 5 minutes to switch cycles. they do not instantaneously go into end all be all mode when they receive out of hour light. It is key to minimize the exposure of light for good growth. Your room should be as dark as a field or forest at night. that being said, if you walk through a forest with a flash light, you don't fool the plants.
I have grown in both situation with complete darkness and some with a bit of leakage. although, by no means should you see a beam of light anywhere near the plants. if there is any sort of beam it should be directed to a wall. Plants are smart. Treat them right and they will do great.
Moreso, If you have some hermies in your room, take a look at what your growing.(genetics) make sure your giving it what it wants and not just feeding the room. Some girls are picky eaters and some are very bad genetics.
Hope this helps guys