Here's my DIY setup:
Front windows are a pillowcase design and slip over the doors with magnets along the bottom and velcro around the mirrors.
The slider has a zipper in the back and 2 rows of magnets in the front where we get in and out (the front zipper in the pic was replaced by magnets after our first trip. Both sections can be rolled and tied up if you're bugless.
The rear has three zippers so you can open up either side, the middle, or the whole thing.
Holy cow, that's a bad pic!
The YKK zippers by the foot came from Sailright. The screen is no-see-um from Home Depot, and the webbing for the borders came from Amazon. About a million hours of layout and sewing, but I'm no seamster.
If I did it again, I would make the webbing and magnets on the slider sections overlap so they would have more positive closure. Otherwise they would well.