Welcome aboard. There is a Mainship sub-forum here where you may get an answer.
There used to be a pretty regular gathering when the company was operating. I attended several in St Augustine and Savannah back in 2000 to around 2005.
There is a pretty active group in the Chesapeake and I think the NE, the PNW and there is also a SW Florida Mainship Group that get together near Ft Myers I believe. Perhaps one of those groups will chime in, most of the organizing and announcements were done on the Yahoo Mainship site before it got clunky.
Sorry I can't supply a contact, you may want to ask this this question on the Yahoo site