An alternate approach is to accept some bullet speed variation, but time bullet exit with the muzzle position approaching the top anti-node so that faster bullets exit when the muzzle is at a slightly lower position, and slower bullets exit when the muzzle is at the top of the anti-node. At some distance downrange, vertical dispersion is minimized by slower bullets having a slightly higher trajectory and faster bullets having a lower one, but for other distances, the speed variation causes an increase in vertical POI dispersion relative to the approach that minimizes both speed variation and POI variation.
No matter how carefully one loads ammo, there will always be velocity variations.
This is the entire point of the Audette. It isolates the exit time that you have described and minimizes vertical POI variations at long range
