Attached is a plot with the HAM5 CPS magnitudes from July 18 (at air HEPI locked) and from 6 Sept when we are under vacumm and the HEPI has closed position loops.  The things we believe are SUS resonances are cleaner now and the HEPI structure modes are lowered in frequency and Q. 

The feature just below 6hz is decidedly softer than the one seen on WHAM4--see comparison in the second attached plot.  All these 'HEPI' features are positioned/shaped differently between HAMs 4 & 5.  Maybe this is external mechanical and I should give everything a good hand-on look-see.