Having flown enough on the L Pad last week, I think the biggest issue, easily trumping density altitude, would have been the wind, or lack thereof most of the time. Getting steady air in the morning practice and officials was pretty much a matter of luck. With even light winds from a steady direction my plane flew just fine, running the same % nitro as home (actually I could have gone down a bit on some mornings). I had crisp corners, plenty of power, etc etc. But just as quickly you could find yourself with zero wind, a (fill in the blank)° wind shift, or a nasty thermal and your plane would be complete junk. It was the erratic light air that shot down Doug on top 20 day, and had Brett displaying impressive agility and speed as he backed up like mad on most of the maneuvers on a qualifying flight the day before.
This isn't a corroboration of the phony physics from a few earlier posts, just my own small observation that performance hinged on much more than density altitude at Muncie this year.