Lead was added to gasoline to increase octane and lubricate valves, A Mini Mac 35 doesn't have any valves. To use unleaded gasoline the newer engines have harder valve seats. The problem with Ethanol is two fold, 1- older stuff used rubber that isn't ethanol proof so ethanol enhanced fuel tends to dissolve some of the older rubbers and plastics. 2- Ethanol absorbs water, water tends to cause problems in fuel systems if it's left to lie around in it.
Friend that is an A&P (Airframe & Powerplant A.K.A Airplane mechanic) tells me must of the STC (Standard Type Certificate) modifications to run autogas in an Airplane is to replace the plastic and rubber to ethanol proof stuff and change out other parts that get corroded by the higher moisture in autogas.
So if you must or want to use regular gasoline with Ethanol don't let it set in the unit after you're done using it.