PING!!!
1, Density, the lower the better for ping, this seems to be a natural variation but the middle of 5 rounds will produce the best clefts.
2, Pressing, there is an optimal pressure for each bat, the key is to hit it, also the method employed to press can have massive difference to the bat, you want a thin hard layer, multiple passes produces a thicker layer with less PING.
3, Grains, the more the stiffer the blade and the greater the energy return.
4, Weight, the greater the dead weight the more willow in the bat and the better the energy return, an easier tactic to employ than Density.