Brian, Northeastern Field Trials on FB covers Horseback trials as well.
This board, which I've been a member of for 12 years now, seems to limit itself to walking stakes, so falling somewhat short for a gold standard imho.

Also, lets face it-the user interface of this board blows. Posting pictures is a bear and activity is very, very low.

If this board is the gold standard, I fear you've set the bar way too low.