When we re make our full cockpit enclosure, which is now due, we plan to have alternate curtains of dark "Phifertex" mesh. It is like large square, very tough, screen
. It would block the flies and mozzies, but not noseeums. We would rely on the finer companionway
screens, in the areas where they are a problem.
If the curtains have very fine screen, there is not enough air. Also, this mesh fabric
blocks a LOT of the UVs, and can cool the cockpit down, while allowing a bit of a breeze. If there are no bugs out, only put in the sunny side curtains, for the 80% shade that it offers, and leave the rest out.
Also, when you take plastic side curtains out, it is best to roll them around a 8" cylindrical piece of upolstry foam, with flannel sheets
between each one. Otherwise they get scratched, and if you just roll them around themselves, they flatten over time, creating permanent waves in the curtain.
Hope this is of use... Mark