Radio Psychedelica

Hmmm...
Has anyone actually measured the speed of propagation of gravitation change?
Everything I've found so far seems to be basing it on the 'speed of light barrier' which smells to me like a assumption.
While detection of gravitational waves has proved problematic, measurement of local graviational fields is relatively simple. Has an experiment been done to measure 'rate of change' of local fields?

This may be limited by the responce time of gravimeters.