Knockback doesn't seem to scale linearly. 80 knockback puts people in tumble and sends them hardly anywhere, but 160 knockback is almost enough to kill vertically on low ceiling stages.
To elaborate on this, the knockback value is not a unit of distance, but rather a unit of speed. Being hit with 160 units of knockback will send you twice as fast
on the initial launch frame compared to 80 units of knockback, not
twice as far.
When you get hit, you decellerate at a (mostly) constant rate, which means that it will take twice as long to decellerate from 160 to 0 as it would from 80 to 0. However, the distance you travel while decellerating from 160 to 80 is much greater than the distance you travel while decellerating from 80 to 0.
If you've done any sort of motion in maths or physics, you might have learned that the distance travelled by an object with constant decelleration scales quadratically with the initial velocity. This means that doubling the knockback value will mean the distance launched increases approximately four-fold, tripling the knockback will increase the distance approximately nine-fold, and so on.