If you have the resources, you could build this or something similar: https://youtu.be/IyV5eQDpqN4. It yields 20 stone/second, assuming you can mine that fast with no lag.
Since my last thread I have achieved a 17.8 block a second gen, but this video defiantly gives me something to consider. I thought 20 blocks a second was just a theoretical top speed. I am hoping that the cmd blocks used are not adjusting the pulse length and can be removed.
Try this one - have it at my outpost. 1.9.4 slowed it up a tidge with the cooldown - but it still places a smack of rocks in the chests. When it is running full tilt - it is 360 stone ((45 x 4) x 2) every down and back, and you are only slowed by your pickaxe. https://youtu.be/jRGqrumOhC8
It is a theoretical top speed, it assumes you can mine fast enough. However, it is suvival-friendly, as the command blocks aren't need for the generator's operation.