To hit the right crude protein for animal feed given two ingredients:
Low protein ingredient A
High protein ingredient B
Target protein content C
Proportion of first ingredient X
X = (C-B) / (A-B)
For example: A is 10% protein, B is 45% protein and C is 16% protein
X = (.16 - .45) / (.1 - .45)
X = .8286
Mix about 83% of ingredient A with 17% of ingredient B.
In my worked examples the high-protein ingredient is insect meal. Figuring out that math is irritating, so I worked it into a simple spreadsheet. I've added values for the animals I've considered so far. If you wish to use it for your own purposes, please make a copy and edit as you see fit.
I will eventually try to formulate complete feeds using a mix of spirulina, BSFL meal and agricultural waste. The goal will be to minimize the amount of mineral supplements since those will be difficult to isolate in space, and to minimize or eliminate grains and other human-edible ingredients. Hopefully most of the nutrients will be captured in the manure waste stream or the harvest waste stream.