I wanted to attempt to make my own high note bocal by drilling an additional vent hole. I have seen some articles mentioning bore size and placement so I decided to go for it. I bought a Fox CVX 3 specifically to destroy and some heat shrink tubing. The drill bit that I used is an Irwin #60, it is 1.02mm.
I drilled through the top of the bocal at both 20mm and 25mm from the tip. Then I set 2 pieces of heat shrink tubing to cover the holes.
This allows me to choose which vent to use and also how much of the vent to have uncovered. So far I have noticed that the vent closest to the reed helps with the notes above high F but the tenor register has an airy rasp to it. The vent farther from the reed helps with notes to high F with less distortion of tone.
With the shrink wrap tubing put in place, the bocal works like normal. So it can be used normally for a piece of music and a vent can be opened for the specific passage that requires it.