Being an old hardware store owner I got to wondering about the screen used in the vent. It's just a piece of screen wire. When you design HVAC systems you have to account for the grate blockage on your vents. So I decided to caculate it.

The screen has 29 strands. Eliminate 2 due to being so close to the sides. Diameter of screen wire strand is .011. As the screen wire plug is also .75, caculate avg length of strand to be .5". Caculate the surface area of a cylinder .5" long, .011 in diameter. Divide by 2 as only half the area is seen by the vent. Gives surface area of .00873 per strand. Mulitply by 27. Gives blockage of .235". Subtract from area of 3/4 vent, .44179 - .235 = .20679" effective vent size.

The holes in my sinks are 1/2". Area of .1963. Difference of 1/100th.

You probably increased instead of decreased the area available in the bigger vent on the labs. Losses to grates are considerable when you design hvac systems for back pressure in the system.

I'm still going to do some tests. But mathematically the only change in vent volume is neglible. I may get out the dremel and thin it a tad. Increase the size I told you for these by about 1-2/100. Mine are just a little looser than I anticipated.