Dylan - I would be concerned that with the small surface area of the pre filter you constructed it would clog pretty quickly. Compare the surface area to that of the filter in the windstar and you will see what I mean.
Have you tried to figure out why the windstar is letting dirt through? It sounds like there is a problem there that could be fixed.
Have you tried to figure out why the windstar is letting dirt through? It sounds like there is a problem there that could be fixed.