I have a 220v muffin fan over the PA cage on top of the KWM-2A mesh lid, and the fan sits on 4 small rubber feet.
Running the 220v Fan off 110v supply and although quieter , its very efficient.
To open cover I pick up fan, place on table and replace after.
I previously had a very small internal fan, but was very noisy and inefficient.
Another method of cooling I want to try is a 12v DC fan mounted to top cover with very thin screws, and supplying it off the 6.3v rca supply from rear, using a bridge rectifier and 1000uF cap in a small plastic box.
Will give about 9 to 10V DC which is perfect for the 12v Fan.
I did this exact mod on the Heathkit HA-14 and its' the charm!.
73 de William, ZS4L / ZS5WC