[knomadd]

It wasn't so much that I read anything, I just saw several pics that they were all mounted flat (or at least appeared to be). I don't think it's so much the compressor that needs to be flat as the air tank. I'm betting it has to do with the drain plug being centered in the tank and not near the domed end. Since I'm using the Porterbuilt brackets, the compressor would be at the same angle as the tank.

There may not be any issues with it. But I'm still pretty sure I'll be happier that I changed it if and when I have to drain the tanks.