After about six years of sporadic effort, I finally finished the W3NQN filter set by building the 10- and 15-meter filters over the past two weekends. Now I can operate SO2R with impunity on all bands. Several band combinations are still problematic, but those are problems that filters can’t solve.
Because the geometry of our home does not permit me to have a walk-behind station desk, I had to attach the filters to the mounting board by laying on my back with a right-angle drill. That sort of thing is always a bit exciting!