I ran a set of COMSOL simulations to determine the dependency of the frequency of each eigenmode on the disk thickness and diameter, within the tolerances. I chose wide ranges: diameter 75.0 +- 0.1 mm and thickness 1.0 +- 0.1 mm, much more than the expected tolerances. It turns out that the frequencies depends almost exactly linearly on both variables: mostly on the thickness and negligibly on the diameter. The following plots shows: the mode shape and frequency (left), the frequency dependency on the two variables (center), the residual of a linear fit and the functional form of the fit (right).

I'm including only the modes that will be measurable by our system (no motion in the center, frequency below 32kHz. Since the disks in my simulation is completely round, I'm showing only one mode for each doublet.