Cab, if e98 is available locally, a brew with some race gas rather than pump swill might make a big difference. I have seen e98 for sale in nw Minnesota and it was much cheaper (according to a friend) than pump e85, and it was available in 55 gal drums. There would be no fed or state taxes on the e98.
If e85 is made with 86 oct, then a mix of 110 race fuel to make e80 , or 20 percent race gas, might push octane to about 113 ? I am guessing on the facts hear, but using the math for mixing race fuels. If there are local ethenol alcohol plants in the area, that might be a source. Info might be available on an e85 race site.