One of my first soaps I made was Olive Oil, Soybean Oil, Cocoa Butter, and Castor Oil--made a super hard bar of soap! I'm going to have to dig that recipe back up because I made it in Brambleberry's lye calc and want to see what properties it has in soapcalc, now that I know how to use it!
Yes, this as well as tallow and cocoa butter. You can us a combination of two or all three if you would like to experiment. I like the 'synergy" aspect of all oils and fats.
I rarely use Palm. Not because I don't like it. Its just that I can source other kinds much more easily. I also give a big thumbs up for Cocoa Butter, Shea Butter, Beef Tallow and Lard. Any of those or a combination added to a soap recipe will add wonderful characteristics!