We made the trek to Bonneville only to find it was rained out. Luckily, while we were there we learned a few things from racers in the area.
Tip #1 To go over 420 MPH, 4 wheel drive is probably necessary to overcome the air resistance.
Tip #2 One engine builder cautioned me that he put 20% nitro in his normally aspirated race engine that previously ran on straight methanol.? He said that he made numerous jetting adjustments and no matter what combination that he tried, the racecar slowed down.? (FYI: another experienced nitro racer said that he was successful at making more power with any percentage of nitro — high or low.? As a result, we are currently researching nitro for a possible future publication to reveal the cause of differences such as this).
Tip #3 The air is thinner and easier to go fast in. This is especially for forced induction engines that can use supercharging to overcome the loss in air density to the engine.