does anyone use 100LL av gas ?

One thing comes to mind, and this is based on my experience as an aircraft mechanic. Av gas burns slower, little hotter and aircraft motors all run a dual ignition system. I do know of a few people that run straight av gas and don't mix with unleaded, however they did have to run different heat range of plugs and change their ignition curve a little bit. It is definitely cheaper than race gas. And as a few members already said, mixed with premium and they have had good results.