I had built couple of W3NQN BPF units for 40 and 80 mtrs. When optimizing single antenna for multiple radios came my mind, my search lead to PI4CC contesting team's High power BPF projects. After reading their construction notes, got some confidence  to build them myself. Peter (PC2A) and others at PI4CC were great help during build of these big BPF units. These are bit tricky to tune as they use 4mm and 6mm copper tubes. Expensive parts are the High Voltage MLCC Capacitors. I used some old spare aluminium boxes and perforated sheets from local market to make enclosures.

These BPF units will be used in conjunction with triplexer on higher bands. Last photo below comparing size of Low Power W3NQN BPF to these units.

 

If interested in building one yourself look at their website https://pi4cc.nl/tech-info/hp-filter/details/