Have you thought about using your SA Castelburn for points? If you already have a points account, then you can deposit it into the RCI points-for-deposit program. If not, consider making a cheap points purchase and using the weeks for this.
Last year I read all I could on the points program, and then I made a buy. Now I am able to deposit my SA Seapointer into a points program and get 27,500 for each of the one bedroom weeks, totaling 55,000 points. Of course, RCI can change this at any time, but I am certainly able to use these points for last minute exchanges and regular exchanges.
Since most of us bought SA timeshare when they were touted here on TUG, we were taking advantage of a currency benefit, coupled with a little known travel destination that was up-and-coming. Later, the benefit of the Australian and other cheap points entry was introduced on this board. So I combined the two to get the best advantage.
Just a thought. The more we learn to play RCI's game, the better our travel experiences.