It's important to remember that the farther you are from sea level the lower Octane required. For instance, in my Corvette, I have a 327 small block with 11.5:1 forged pistons. At 4000 feet elevation, I can get away with 92 Octane Chevron. However, when I take a little drive towards the coast, I'm looking for Octane boost just so she'll idle. I did try and use 85 Octane once, but had to siphon it out and add the good stuff, as it wouldn't even idle.
Same goes for the 500. Higher elevation means the bike is less sensitive to Octane rating. I used to run VP exclusively, riding and racing. After several years, I switched to 92 Octane Chevron for the bike. If we head for Southern California for a race at sea level (or close to sea level), we step up to VP one again.
Rick