Do you want to build a porch or a deck? Do you have a BoWrench? Do you live in the South?
You can have your screen under the floor and use your BoWrench too. I bought a 25' roll of 3' wide 20x20 mesh fiberglass screen and tacked it to my beam, put down a board, rolled up the screen to fit between the parts of the Bowrench and proceeded like normal.
It gets kind of saggy underneath. I will probably have to go under there and staple the joints up to the bottom of the 2x6 where it overlaps. But it's a pretty good compromise. The floor boards running straight is more important to me than how taut the screen is underneath.
The price of the 2x6 floor and the screen is only a little less than what I would have spent on 1x4 tongue and groove pine, but I would have needed two more joists and I couldn't just run Deckmate screws into it. I don't think I could balance a floor stapler on the joists even if the staples would stand up to outdoor use in pressure treated lumber. Instead of a pretty little porch floor I have a very strong 2x6 deck that I can fix up nice with Minwax 2 part wood putty and solid deck stain. And maybe screen in later.
I have heard of 5/4 tongue and groove kiln-dried-after-treating porch flooring, but nobody around here makes it or sells it.