I will play as I finish packing for tomorrow....
So you need to know the density of Cream of Coconut which is about 10.16 oz per US cup (I had to look that up). A cup is 8 oz as you know.
Density = mass/volume, therefore volume = mass/density
Volume = 8/10.16 = .8...this confirms your 15 oz weight = 12 fluid ounces
You are measuring the other 2 items by fluid ounces so my vote is to go with 12, 12, 48 fluid for all ingredients
Having said that I usually mix the mixers and then adjust by taste...:)
Your OCD friend....