The problem with putting screens on the windows is that if there are bugs, there is usually heat, which means you want as many windows open as you can, that means screens for every window, on top of that, if you are trying to keep bugs out that means you are camping in the truck, so you are going in and out. Every time a door gets opened, the bugs get in.
For comparison, we just have a $6 queen bed sized mosquito net, it's kept in a zip lock back in the back cargo drawer, weighs nothing, is never in the way. The few times we need it, it gets unfurled and attached to the inside roof of the truck. All windows open, lots of venting, no bugs.
With a net it hangs just where you need it and you lift up a corner to get in or out, very few bugs get in that way and the net helps to wipe any bugs off you.
In our case we have that elastic cargo net on the ceiling, so we just keep clothes pins in the mosquito net bag and clip it to that. You could just as easily keep a few magnets in the bag and just stick it to the roof with those when needed.
Much better and much cheaper than screens.
So, no screens.