I needed to produce some referance power levels that were 'down' from
my calibrated 0DbM generator. (It's output power is auto leveled, and
non-adjustable) 9445mhz, center of one of the maritine radar bands.

I've never worked in this band, but recall that some lower-frequency signal
generators use a "waveguide beyond cutoff" attenuator. If you can find some
waveguide sections designed for a sufficiently higher band, the attenuation
will be proportional to their length.

This doesn't address impedance mismatch, but neither does your method.

73, Fred, K4DII