I built the 30M W5USJ LPF from the chart, next. You'll notice on the chart that the input and output impedances for this filter are close to 50 ohms with little differences. My tests showed the same--45 Vpp? (5W) output either way. That indicates if one can design the trap filter for close to 50 ohms, then the filter is indeed symmetrical. Too bad Chuck Carpenter is not still around so we could ask him if he noticed the impedances were the same for this filter and not as close to 50 ohms for the others.
73,
Steve AA7U
