Posting some initial plots of SPI DIFF L, doing my best to line up with my results here with alog 73976, where Jeff looks at IMC F length in hz/rthz and compares that to ISI motion. On the attached image, I show spectra for the differential HAM2-3 X super sensors (calculated online in seiproc, using blended cps and gs13s from each chamber), HAM2 and 3 X gs13s and IMC F, all calibrated to hz/rthz using Jeff's factors from 73976. H1:SPI-H23_DIFFDISP_MAIN_OUT_DQ is also calibrated to hz/rthz using the same 70.551 hz/nm Jeff calculated for the ISI. With that calibration, SPI DIFFDISP is still off from the other sensors by about a factor of 3. 

For the second image, I made a new copy of Jeff's template from 2023, re ran it for last night and added SPI DIFFDISP. We don't have CARM yet, so it's not complete, but I updated references. Again, I used Jeff's 70.551 calibration factor to convert SPI DIFFDISP from nm to hz. SPI seems to agree better here, so I'm not sure what the differences are from from first plot.