[Tom Goldman]

Asking what the best pinion angle is , is like asking a racer what the best brand of beer is.
everyone has their favorite !
Realistically you have 3 basic groups when it comes to pinion angle, 1,leafspring with caltrak or slapper bar, 2 ladder bar ,and 3rd , 4link type suspensions.
As you discovered what works best for you differs from what others may use... Why, because spring rates ,shock settings and radial movement of the suspension will all influence the effect pinion angle has on the cars launch.
Idealy the sweet spot is one that utilizes the least ammount of pinion angle while the car is under acceleration, think less bind.
After years of setting up chassis, I've found Ladder bars like between 1.5 to 3.5 deg.
4links usually 2-4 deg. and slapper / cal track type 3 to 6 degrees.
As they say your results may vary.