Can you link the warranty statement that states using E10 will void the warranty? I think the owners manual only specified no more than 10% ethanol in the past.
Frankly, I would just use E10 and if they asked what gas you used if a problem arises, I'd LIE and tell them ethanol free because they have no business selling equipment in this day and age that can't handle E10. I got my current blower, at least 6 years ago and have ran nothing but E10 every season, have never had to do anything to the engine (including carb) except tighten the carb mounting bolt back down a couple years ago when it vibrated loose.
It is very doubtful there is anything *special* (craptacularly poor) about their LCT engines that they can't handle ethanol as well as any other ~half-dozen HP blower on the market. Medium sized outdoor equipment engines are far more tolerance of E10 than the tiny ~30cc size you find on handheld equipment.
Stay-bil, not really needed unless you intend to store it over summer without draining the fuel or use fuel you leave sitting around more than a couple months if E10. Ethanol or not, you're best off draining the tank and running the engine till the fuel line is empty at the end of the season.
Anyway, here is what LCT, the engine manufacturer has to say about it:
http://lctusa.com/product/stormforce-208/
Engine Fuel
Minimum – Regular Unleaded 87 Octane Gasoline (max. 10% Ethanol blend can be used with LCT engines). E15 to E-85 can NOT be used.