Scott, I agree on the book not always being correct. It seems the different track on the Cobra makes the generalities incorrect.
ozaiss1, did you adjust all four tire pressures or the fronts or backs only. More pressure inthe front or less in the back will help.
http://rogerkrausracing.com/overundr.html may help.
Stiffening the chassis wil always give you a better baseline for making adjustments.