Jon, after Celestron and Losmandy developed the G11 introduced in April 1992 (just in case any one wondered where the "492" came from) they announced the G9 model, a C9.25 on a modified GM-8. The mods were using a G11 saddle and an inadequate copy of a Vixen AL110 tripod that first served as the CG-5 tripod. The Tripod was complete with the CG-5 hub that had been drilled for a Lomandy made adapter. I noticed that there were some extra threaded holes in the adapter which lead to this discovery.
As far I can determine the HD Field Tripod was never offered as an?option with the G9.