[Paulo]

You guys are confusing two different setup angles. The '21 degree' is how the beater shaft sits relative to the holder, this is a fixed value.

45 degrees could be the angle between the beater shaft and the bass drum head when rested. Which, before the 21 degree thing, would have put the shaft perpindicular to the beater holder. Or it could be the angle of the main beater bracket to the horizontal plane of the pedal.

Either way, what the 21 degree angle gives you, is a beater strike sooner in the stroke of the pedal, than previous, considering equivalent distances from the head for each respective pedal example. I've designed a similar intent into my 'custom' beaters I made a while back. And it does make a very considerable difference in thud.