I wonder, could your friend measure Fr with a signal generator and DVM and then cut the hole larger as needed for tuning? Or maybe it's just easier to use the formula below to find the hole size. Either way, I'm thinking that probably the port hole is going to be very short, so using panel depth for the port length may be your friend's best option.
One way to give an attractive smooth look to the port is to laminate it with a thin plastic strip. Sign makers have just the stuff. Formica might work too. Another thing I personally like to do is to paint the edge.