Fatfingers, Nice Job!!
You could also use a prefilter and filter instead of using the segregated fan. A household heater filter from Wal Mart for $2.00 ( cut to fit a little larger than your opening and a thin piece of foam over that for a prefilter )would work great. Or check with your local paint supply and ask how much a paint booth filter roll would be. I think the idea of using stainless steel would be awesome, but the cost would be cost prohibitive.