The difference from 2.4 to 3.0 is vast. The run really is just too low at 2.4. Even 2.6-2.7 is painfully low.
3 feet was absolutely an optimum flow. All that Class II-III stuff that's junky and low quality turns into super fun, manageable Class III-III+ bedrock goodness. Flight Simulator is much better, and other than stickier holes, the mini-gorges are better too. Solid Class IV run with 3 IV+ish spots (the two minigorges and the big one).
If any of the powers that be are reading, I strongly suggest that we urge Duke to always run it at 3 feet when possible. It takes a mediocre run in a pretty place and turns it into a stellar run in a pretty place. This isn't flow snobbery, it's just plain truth.