No you guys misunderstood. I used foil tape inside the meter lens. look how even the lighting is now. It was darker at the top because of the light loss and now its very even. Hell no I wouldn't cover the vents on the case!! Do you think I'm crazy?
You are covering the top vent... with your preamp!
In your image, you are showing what I assume is a preamp sitting right on top of the 400, that's a bad thing to do, especially in an enclosed stereo cabinet. Look at your preamp, you have probably a 1/4" space between the 400, heat is just going to build up with nowhere to go
This is just MY observation, I have been known to be wrong most of the time. I do know my amps would be a smoking hulks if I ran that setup at the volume levels I am accustomed to