Sounds like a NO-GO!
Give Terry Goode at Collector's in Pelham a call. If he doesn't know about it or isn't planning on being there, you can bet it's not going to happen. [Terry rents lots of tables at ALL MA/NH shows, so although he has NOTHING to do with planning the events, you can use him as a barometer.]
Setup for the gun shows is the Friday before (today!) starting in the early evening, so it's more than "a bit late" for the promoter to not get back to the host site!!