People running higher ethanol content should install an Ethanol Content Analyzer. I like this one from Fuel-It. It is Plug & Play. Just swap out the OEM fuel line with this one and connect power/ground and get real-time ethanol content % and fuel temp. No guessing or messy measuring at the pump.
https://www.fuel-it.com/ford-f-150-3-5l-ecoboost-flex-fuel-kits/
That looks like a nice kit, but would it really help people that are mixing EXX tunes? You wouldn't know until after you've filled and put on some miles before you would know what % you have and wouldn't really be able to correct it without loading a different tune if it's off. Or am I overthinking this?
I'm curious about E tunes and would like to try one, but almost thinking I'd rather just update the HPFP or injectors and try to run straight E85 (or whatever the pump is) than worry about trying to mix the right %.