What you'd be best to do (if you can) is wait until winter rolls around to tune the car for E85. Try and get the tuning done on the coldest day possible (when the cylinder charge density and inj duty cycle will be highest), and then do the on-road tune finish in, again, the most arctic temp you can get (most likely at night).
As most would know, the winter 'E85' blend from Caltex contains the least ethanol. I emailed them a while back to ask what minimum RON rating they specify for E-Flex, and the fuel science guy said it's 105 winter and 106 on summer blend.
Done this way, you should be able to ensure the tune is peachy year 'round.