Here's a quick analysis from what I was able to glean from Mark's spread sheet and Doc's info, and incorporating Sumner's spread sheet.
w/2.14s @5285 we’re at 204
Spread sheet says 5307=205
5285/5307=.9959
204/205=.9951
We’re talking .08% difference, so we can eliminate any slip in the drivetrain, and reasonably assume any other numbers we generate should be accurate.
The Purple line was the power band used in 4th with 2.14s.
The Australian Non-Lucas Electronic Yellow line was the power band used in 4th with 2.41s.
In short, you spent less time in the area where the power was hanging out.
What IS good news is that by hitting the wall with NO WHEEL SLIP, we can take the HP figure at that RPM and calculate your drag coefficient.