Using Lisa's updated H1 optical parameters from LHO:13815, and also the as-built positions of the HAM6 optics, I've made some beam propagation calculations for the AS WFS and the beams on ISCT6.  The script and the parameters file are attached.  Here are some things to note:

• The mode matching into the OMC is 87% for a single-bounce from ITMX and 94% for ITMY.  This is in agreement with Lisa's calculations, and as she pointed out there is a lot of sensitivity to changes in the SR2-SR3 path and the mirror ROCs.  These numbers are still just a model, but if we want to measure the true beam that will be hard because...
• The beams coming out of the vacuum (ASAIR and OMC-REFL) are both diverging somewhat quickly, the Rayleigh range for each is about 1.2 meters, and the waist (~0.63mm) is in the vacuum shortly after the beam is transmitted through OM1 (for ASAIR) or reflected off the OMC (for OMCR).  As a result, any propagation calculations that use beam profile measurements on ISCT6 will be very sensitive to the distance from ISCT6 to the in-vacuum optics.  I think errors of a few centimeters between, for example, ISCT6 and OM1 on the ASAIR path will skew any propagation calculations, and errors of this size are hard to avoid.  If people have any ideas for making beam profile measurements on ISCT6 please let me know, at the moment I'm not confident that any measurements of this kind are worthwhile...  (When Chris M. measured the beam at L1, he took a few data points inside the chamber, on the other side of the waist in the beam from the SRM -- see LLO:8182.  Without data points that include the other side of a waist it is very unlikely that a fit to the profile will give a reliable estimate of the beam parameters.)
• The waist in the AS WFS telescope (in-vacuum) is very close to AS WFS B, for single-bounce beams from ITMX and ITMY.  The spot size on WFSB is about half the radius of the spot on WFSA.  This agrees with what Koji observed in the chamber.
• The Guoy phase of the OMs is a little different than what we expected using the nominal beam in T1200410, we need to think about how this affects the control topology for the OMC and AS WFS centering.

Here's some data:

I attach plots of the ITMY single-bounce beam path for the OMC and for the AS WFS.  The locations of the in-vacuum components were calculated using the closeout photos that Koji took before we closed the chamber; they are here and here.  The path lengths between optical elements are probably subject to errors of order a centimeter.