Originally Posted by vettenuts

I think the answer above provides good information. The reason I was looking at it was to increase stiffness of the pushrod taking into account the weight I would be adding to the valve train. If the stiffness/frquency is pushed high enough, harmonics within the pushrod won't come into play.

Given that, flex does come into play. The pushrod can still flex without reaching its first harmonic. It is possible to have a pushrod that has its first harmonic above the range that would be excited within the valve train, but the flex would cause issues with valve bounce. Therefore, the stiffest pushrod you can fit in without having valve float is the better solution. I wasn't sure the double taper would fit when I bought them but rolled the dice and checked them out once I had them in hand. They cleaned up my upper RPM quite a bit. I wasn't looking for a hp increase, rather better valve train stability to prevent issues with valve bounce which will wipe out cam lobes and lifters.