If you choose to cover that board with material, make sure its a UV stable product. Otherwise the sunlight will eat it up.
And while you're back there, do consider a high mount/3rd brake lamp addition.
Limo tint rear and side windows here, so on my car it didn't matter very much about the material. :D
Now on the Wife's 72 with no tint I expect that speaker cover material to be 3 shades lighter by the end of next summer.
