"He who marches out of step hears another drum." ~ Ken Kesey
4' 2*4 with 2*2 chunks as spacers screwed into it. Screen, 2*2, screen, 2*2, screen, ect. The 2*4 puts the screens at a nice angle for draining. The 2*2's slave them out nice, and as long as you insert the corner of the screens between the 2*2's, they provide enough support to keep them upright.
Inspired by gkitson's racks http://www.theshirtboard.com/index.php/topic,13007.0.html
I use the same racks for both, no issues at all. Each fan has a filter on top that I change when needed. The screens dry to the point of no drips within about 5 minutes, so as long as you are going left to right or right to left on both levels and start on the top, no drips. I haven't had a pinhole or snake eye since I started using it...