I have a PM 50, probably all you'll need also. I decided, hesitantly, to put it on the side. I dont have any issues with water coming through the screen there. I thought that if I put it on the top then that would cause more leakage. Plus the lights would get it in the way. As for the washers it will probably make more sense when you see the misting nozzle. Its a threaded nozzle with a plastic nut on it. Take off the nut and put a washer on. Put the nozzle through the screen. Put another washer on from inside the cage, screw the nut back on. Done. One thing I did though is bought a little spool of generic wire at Lowes. Its great for tying things down on the screen. I had to tie down the tubing to the nozzle as when the pump is on, it vibrates shaking the cage, but not so much if you tie it down.