If the weather is good I would try to target the trout and reds in the creeks to the South of Horseshoe around Shired Island, with the moon being full it will push more water in the creeks and allow larger boats to get back into the potholes were the trout and reds like to hide. The full moon in December has not been a good time for me to target the Red Grouper in the past because they start to move out to deeper water and the Gags like to move in to the shallower water. I think it would be a waste of fuel and bait just to find out that all of your offshore spots are full of Gags and not Red Grouper or even worse the endangered American Red Snapper.
You have a -.6 low tide at 9 am on the 28th. If you have a ne wind you will not have water at all. All day. If you have an airboat you will kill them. If not, you will not get your boat off the trailer. If it is cold you can head up to Steinhatchee and catch all the trout you want in the river. The red grouper will be in 50+ foot.
Pending conditions, any chance of a good bite down there late December? Would be there during the full moon Dec. 28th???
If so, what to fish for? Trout & Red Grouper?
Sail cat what type of boat are you bringing? If an offshore boat with the tides that Scott Crown found for you I would be very careful inshore but focus offshore if the weather allows. As noted, the RG will be deeper, find the hard bottom in 50 to 60 to start. Cannot keep the Gags which makes 20 to 50 a waste of gas unless you are happy catching BSB and Grunts. Size down the tackle and have a blast. BSB is better on the table that RG IMO. There is a cut or channel east of pepperfish keys to the north of HSB that hold trout depending on the temp during the winter if you cannot go offshore.