I have a squirrel cage fan with a 9" intake opening. The fan (with motor inside) is 18" long x 17" tall x 13" deep. I plan to make a rolling cabinet which houses the fan and stands about 38" tall, but it seems most air filter systems for shop use are off the floor. Is there an advantage, other than saving floor space, to having the filter hanging from the ceiling? My shop is a two-car garage 20' x 18' x 10'. Any suggestions on the best filter and size of filter for this fan?