Combining flours to raise the protein level
I have some bread flour with 12% protein and another quantity with 14% protein. Using simple mathematics I can calculate the right mix of the two flour quantities that would give me protein at a desired percent above the 12% and up to the 14% levels. For example the ratio is 13:7 if the target combined flour would have 12.7% protein or 2:3 if the flour would have 13.2% protein.
However, what other factors should be taken into account when combining similar flour types, but of different protein content?