On the second disk of Dream Theater I brought to Tom's the guitarist talked about his baffles; he uses six full stacks, and the plexiglass is flat, with a hole cut in them for the mics. He doesn't use them to cut down on the sound on-stage, however, he uses them to keep his amps "clean"...
...the drummer spits like a camel (you can see this throughout the show)! :x