My sil (also dvc member) and I took a chance on Sunday and called MS. We wrote down two places in Williamsburg, VA, two places in Marco Island and 6 places in Sanibel Island. I told my sil that we would not get anything this late (for the summer). We gave them a three week span.
We had done some research and we checked each one with RCI, TUG and Tripadvisor. I told MS we had a list. He basically told us there was nothing available in Florida for the three week period we gave him. He had one place in Delray and another one (began w/W) in Ft. Lauderdale.
I was worried about calling with a "list" - MS was very helpful and patient. After a lengthy phone call, we ended up reserving Vero Beach and WLVs. I hope you are looking for an exchange sometime in the future. The further out, the better your chances are.
Good luck and let us know how you do. Looking forward to hearing positive experiences with the whole RCI trade.