Perhaps someone missed this along the line

PCBs unless they are drilled to alow cooling will restrict air flow under the chassis. Wires will not restrict airflow to such an extent. Leaking electrolytic capacitors cause PCBs to become conductive, with the voltages present in valve amps this could easily cause a fire with the PCB going up in flames.
Take it from me i have seen what high voltages & leaking capacitors do & it's no laughing matter
Do i need to add anything else or have i said enough?