You could change that to being:
coconut 15%
Caster 5%
Shea Butter 20%
Palm 60%
And you are at 4. If 4 was very much the magic number, I would keep the castor and not the olive as in the recipe above. However, if you could go to 5 oils then I would make it
coconut 15%
Caster 5%
Shea Butter 20%
olive 20%
Palm 40%
Soaping (well, GOOD soaping!) is all about balance. We want some of this in there, but this means that we need to consider x and y. If we put in some of oil x, it then affects something else.............. it can get tricky if there is a particular combination that someone is heart-set on using, but other than that a balanced recipe isn't too tricky once you get a feel for some of the major oils and what you need to be mindful of.
^^This!
The reasons are:
Shea Butter will cut your lather if you use more than 20%. 20% will still harden your bar, and give you a lovely soap. However, if you use more palm, you won't need this for hardness. I would try a batch with shea butter, and one without, then see what YOU prefer.
Increasing the palm will give you a harder bar. Palm/lard/tallow provide fatty acids that help the structure of the soap, as well as the
skin cleansing without stripping benefits. To me, this is the most important part of a soap. If I get this right, everything else sort of falls into place much easier.
I can add coconut oil/palm kernel oil in the 10-15% (my personal preference, yours may be completely different) range for extra bubbles without drying my skin.
Then I can add olive oil/rice bran oil/sweet almond oil in for...I really don't know how to explain what those oils do for soap, so bear with me, please. They make the lather almost seem more luxurious. Soap without something in this oil slot is not really harsher, but it is just soap. Nothing to get excited about. With at least 10-15% (again, my personal preference, yours may be completely different), you get a richer lather. It is definitely noticeable when you leave it out. I do NOT like high olive oil soaps. They just are not my favorite soaps.
Then there is castor oil. Castor oil makes your bubbles hang around longer. This makes the difference of how long that lather lingers on your skin. I prefer 5% added to every bar soap. I have tried more, but I see no change until I get to 10%, which I don't like.
Then there is the superfat amount (not added in after trace like in HP, just changed on the
lye calculator). My personal preference is 5-8%. Again, you may prefer higher or lower depending on the recipe you make.
Then I would add a sugar. I, personally, use white table sugar or honey. But people use milks, cooked down beer, cooked down wine, and other things that contain sugars. Sugars help boost the bubbles in soap. I prefer to use between 1 teaspoon and 1 tablespoon PPO.
To sort of boil this down, here is what I would do without specifying exacts:
Palm/tallow/lard: 40% or higher
Olive oil: 10-15%
Coconut oil: 20% or lower
Castor Oil: 5% always
Superfat: 5-8%
Sugar: 1 teaspoon to 1 tablespoon PPO, OR milks, beer, wine, etc
Then you can add any butter or "luxury" oil that you like. If it is a butter, then decrease the palm a little to accommodate, if it is a liquid oil, decrease the olive oil a little.
To tweak this to your personal preference, I would change 5% at the time. Up or down, and try each batch against one another after the 6 week cure. You will then figure out your best recipe. Be sure to label your batches and keep your recipes with the name of the soap and the date (add your color blend and scent blend information). Then write on the recipe what you thought of it. This information becomes invaluable when you've made many batches of soap. You can then look back through them and see what you've done, and know what you thought about it at that time.
ETA: Sorry about the wall of text, but I can't shorten it and still convey all the info.
Thank you for taking the time to look at my new post. I'm in desperate need 
