Kathymzr, last year I took some salt soap with me when I went to Hawaii to test it out in your humidity. Hawaii's humidity is different than it is here in my part of Illinois.
The resort where we stayed was without AC of any kind, only ceiling fans in some of the rooms. The bathroom, however has no ceiling fan. Because we kept some windows open for air-flow and so we could smell the flowers outside, the humidity was pretty much the same indoors as it was outdoors. And I kept some ceiling fans running while we were in the unit as well. Anyway, the reason I mention all this is so you will get a picture of the actual environment for the soap, although you probably understand this better than anyone who doesn't already spend a lot of time in Hawaii.
The salt soap was made with 100% salt (same weight of salt as weight of oils). The soap was still fairly young and not cured as long as needed for a salt soap, but I wanted to test it out in Hawaii's environment. In fact I intend to do that again in July with the same soap (same batch, but different bar, of course.) I don't know if we will have AC in July or not, though. Probably not.
Even though the soap started out dry and sat on top of a self-draining soap saver, water beaded up and pooled on top of the soap as it sat in the bathroom. I periodically would dry it with a dry cloth and it would repeatedly attract water. It was a very large bathroom and not any more wet than the rest of the unit, so it wasn't due to added shower or bathing moisture, IMO. And it was only one of two bathrooms, so it wasn't even the only one we used.
Here in Illinois with AC, the salt soap never collected water.
So that's something to be aware of when you choose they types of soap recipes you will be making. I supposed high salt content would be out. Also, I think you'd have to avoid any type of humuctant as an ingredient as well. Avoiding adding extra glycerin would be necessary for that reason.
