Hi,
I use palm oil and palm kernel oil with olive oil. Palm kernel is similar to coconut oil but will give extra glycerin to the soap.
Also, shea butter, cocoa butter, and mango butter will give you a harder bar if you don't mind spend a little bit more.
The longer you let the soap cure, the hard it will be. Most reading materials tell you to wait for 30 days but I cure mine for 3 months.
Good luck!
C