2-E and COR

[Kumabjorn]

At the beginning of 2-E HK states that COR for better golf balls are 80% but it drops below 70% at higher speeds.

Is there a "diminishing return" on higher driver speeds? In other words, if my "controlled" driver spped is 108 mph, but I can get it up to 111 mph (with various results) the extra 3 mph just isn't worth it?

Second, are the 80% and 70% figures valid even with modern balls like Pro V1 or HX Tour?