IN VACUUM beam heights are ALL 5.5"  This is measured from the top of the optical table to the center of all TMs, mirrors and other optical components. This beam is ~36" above the floor.

PSL (inside of enclosure) main-output  beam: PMC, MZ, RC and ISS  are at 3" heights. IOO Angle & Position, MC-Trans and RFAM qpds are at 4"

ALL OTHER beam heights at atmosphere and  different ISCT (interferrometer sensing, control optical table)s are at 4"