I run inferred flex from Dusterhoff. I do not race on pump gas but I do beat on it occasionally. It's been to the track on the flex tune but only with good ethanol in the tank with the alcohol inference stabilized prior to arrival of the track.
I'll blend & test or math things out until I have over 80% in the tank then switch to the 2.50 and dedicated E85 tune. And doing this since late 2019 and roughly 24,000 total miles.