After Steve pointed out the 'deep hoop' issue, we decided to examine putting an RF Amp on the PSL table, between the RF combiner and the triple resonant box.
5) No proper stuff from Teledyne Couger
By looking at what Daniel used in the low noise EOM Driver for aLIGO, we found the A2CP2596 from Cougar.
G = +24 dB, NF = 5 dB, Max Out = +37 dBm. It comes in a 2-stage SMA connector package. I've asked Steve to order 2 of them with the appropriate heatsinks.