What bearing would or could Lorentz-Fitzgerald length contraction have on Ligo detections? Was this accounted for?
Special relativistic length contraction due to relative motion of the source and LIGO has no material effect on the detectability of a source.
The detection principle works by looking for a change in the length difference between two perpendicular interferometer arms, that is modulated at the frequency of the gravitational wave.
Seen from Earth, the relative motion just means that the signal is redshifted or blue shifted to a different frequency. This redshift cannot be determined from the LIGO observations alone, since the rest frequency of the source is not known.