Decks, Patios, Porches and Docks - Screened in porch flooring ?

We had a standard wood deck on the back of our house. This summer I took on the(huge) project of converting it into a screened in porch by myself. Gable roof with a cathedral ceiling and the whole bit. The only thing I have left, is the floor. It is now the original presure treated deck boards with 1/4" gaps. I want a finished look to the floor. I considered 3/8" plywood with indoor/outdoor carpet. This works out to about $1.33/sq.ft. because the price of plywood in our area has doubled. For $1.55/sq.ft. I could have tongue and groove wood floor and look about twice as nice as carpet. Now to the question. Since I already have a nice wood deck floor, is there any way I could fill the 1/4" gaps with putty or something, sand down even, then solid color stain the whole thing, giving the look of a solid wood floor ?
Underneath will have a ceiling, so keeping bugs out is not a concern, but the "look" of a nice floor is.
Thanks, Steve

Unless supported from below anything in the gaps will eventually fall out. You can put down the thinnest plywood you can find if you are going to carpet, the deck boards should be planty strong and even 1/4 inch plywood will bridge 1/4 inch gaps.

Don't feel like the Lone Stranger -- the cost of your plywood AND EVERYBODY ELSE'S has doubled!!

Like brickeyee said, the decking will support whatever you put over it for a solid surface for the carpet. 1/8" Masonite would work. Or you could lay down a pad and use laminate flooring.

But trying to putty in the 1/4" gaps between the deck boards? NOT an option.

Thanks guys. I was afraid the gap fill wouldn't work. That narrows it down to carpet or tougne and groove.