I have been playing again and made a 2.4GHz ID filter.
The top line is with a back to back connection and the bottom trace 10dB per div vertical and 50MHz per division Horizontal.
Not brilliant as I guess loss is around 1.5 dB. It still could be useful between a driver stage and main PA for DATV to clean up things before the output stage.
I am pondering placing a few more screws in there to allow a small change in the coupling between stages, but not sure if it would give any benefit.