Hi Cre,
I grew up at Barraba just north of Tamworth but used to sail in the 1990's up there.
We used to sail/camp at Chaffey Dam which is 30mins towards Dungowan but the wind is unreliable.
Also at Split rock dam which is just out of Manilla(about 45mins north).
Sailed at Keepit a few times but more skiing boats to contend with.
I guess the good thing with dams is you can get cross shore somewhere as long as you can get access the most spots around the dam.
The main disadvantage is the wind is usually gusty and unreliable.
Not sure if many people sail up there anymore, maybe a few?
Find a friend that owns a ski-boat as waterskiing is awesome up there,and take the windsurfer as a backup if the wind comes through, then save your holidays and head across to the coast to port stephens/port macquarie/Woolgoolga/Newcastle.
Good luck