My current bracket E85 motor is right at 15.00 to 1 due to the used heads I bought to use having 60 CC combustion chambers instead of 76.00 that the Indy 440-1 come with, my mistake for believing the seller and not verifying the actual combustion chambers sizes before ordering the custom Diamond pistons
I wouldn't worry about the compression ratio as long as the fuel you buy is always E85 or higher, not like the winter mix is here at E75
Any compression ratio under 13.5 to 1 true mechanical ratio should run fine on E75 also