I've been a bit busy gutting and rebuilding my power/SWR meter. It now has all new innards which should give more accurate performance over a wider band, maybe 10-150MHz. The schematic below shows the circuit I used. The two transformers are wound on Micrometals T44-2 toroids.
...Aaaaand here's a dummy load I threw together to test/calibrate it with. My NanoVNA shows it's good to at least 150MHz (VSWR <1.1), and probably ok to dissipate 10-20W for short periods. Oh, and it has a diode/cap so I can double-check power levels using a multimeter. I've since put it in a sealed tin so that one day I might fill it with mineral oil if I ever need better heat dissipation.
So with that, I turned up the PA to 2W (oooooh! I hear you cry...). Happy days.