The nearside bracket of my PA has 1/2" hole in the third position from the top amongst the line of 1/4" holes. Is this original or the work of a previous owner? Not really important but I'm curious.
I HAVE restored a PA recently and can say with certainty that mine have no such hole. All holes are 1/4 inch except for the top one which is a little larger to accommodate the brace rod lug. The only explanation I can think of is that someone drilled it out to mount something there. On my PB Airline, the cross braces are moved to a lower position so that a tool box can be mounted on top. But I didn't think that they needed to be lowered all the way to the third hole. Perhaps a convenient place to pass a pipe union through for a supplementary gauge?