Another thought would be
20% CO
35-40% Palm Olein
30-35% HO Sunflower Oil
5% Castor Oil
10% butter if you want to add some but it is not necessary. Adjust above numbers
RBO is not necessary and will darken the color. Personally, I do not like RBO but that is me. I love Sunflower in soap. I use 40% Palm Oil in my vegan soaps and looking at the fatty acid profile there is not a huge difference between the Olein and Regular Palm. If you go with 40% Palm or Palm Olein I would recommend a 30% Lye concentration if you want to do swirls and keeping the castor oil at 5% or less. Castor accelerates trace even with a 2% difference. High CO soaps are very soluble and will not last long, which is why they lather in salt water.
I did an exact one a few days ago (minus the Butters). HO Sunflower helped me get some nice drop swirl.
What happens if we use Palmolein over 40%? I used 45% yesterday (along with RBO, CO and Castor.)