I do not advise Shea, butters really kill the lather in Salt Bars. My go to salt bar, which I have made for several years is 85% Coconut Oil, 10% Castor, 5 Sunflower or other soft oil, 15-17% superfat, 30% lye concentration with 85-100% fine salt. Make sure you use fine salt anything else is to abrasive. I set my out and cut within 1 hr. I am not one to gel but with salt bars you really will not see a color difference and it is easier to monitor if it is out on the table. They need to be warm when you cut, better yet individual silicone cavity molds work well.
Over the years I have tried many different combinations of oils, and butters trying to come up with a less soluble salt bar but end up grinding them up and returning to my original formula above