For a starting point I'd just use the high-end AI estimate for serum level variation with pure testosterone acetate of 60% above and below the mean. As expected, this is larger than the 50% figure I usually use with propionate. The target variation is 25% above and below the mean. Solving the equation leads to testosterone from the longer ester comprising 1.4 times the testosterone from acetate.
Testosterone enanthate is about 72% testosterone, whereas testosterone acetate is about 87% testosterone. Therefore you're looking at about 1.7 parts enanthate to 1 part acetate, or roughly 5:3 rather than the 4:3 used with propionate.
To reemphasize: this is just a rough starting point and you'll need to take measurements to see if adjustments are needed. Also, this ratio is by ester weight, not volume. Enanthate is usually going to have at least double the concentration of acetate. For example, if the acetate is 100 mg/mL and the enanthate is 200 mg/mL then the volume ratio of enanthate to acetate is 2.5:3.
