On Aug 29 & 30, while at vacuum, the elevations of the HEPI piers were measured with Optical Auto-Level--LHO aLog 38584.  On Sept 20 and 27, the HAM Piers were measured again--38776 & 38810, now with the Vertex was at atmosphere.  Today, after the Vertex (sans HAM6) is again under vacuum, the piers were sighted again.

The conclusion here is while there are some changes while vented and when back to vacuum, the most is a few tenths of a millimeter and amount to ~100urads of tilt in the worst case.  Not necessarily tiny but not horrible.  Attached are my surveying notes from today and the deltas from before, during and after.