It will work fine. Stoich is stoich as far as the O2 sensor is concerned. O2 is one of the better sensors on the car as it works from basic chemical principles.
The biggest issue E85/E70/Eflex users seem to have is the changing ratio. If you want to be really special you can make a flex fuel vehicle with an oxygen content sensor in the tank (http://www.zeitronix.com/Products/ECA/ECA.shtml) and an ECU with multiple maps (Link G4) and interpolate between them.
I say just run 98 ron. That giant ugly turbo you have will make plenty-o-powah.