I know more about the noise and issue with this car than most others.
If ear plugs or headphone are legal that is the best option I could find.

If you have the SPL versus speed, then that will highlight what sort of power you will need to equal, or exceed, the noise.

Then With the ear plugs you at least get ~20 dB of noise suppression, which is a huge bonus.

You really only need a strip of dynamat under each seat, and the rear. Literally an 1" wide "X" will do most of the job.

I take it you use it for touring more than sports?