I have mixed feelings. If this had been done 20 years ago, I think it would have been advisable. My understanding is that the current ball is no hotter than balls that were available in the early '90's, but that those balls were too hard to be playable by most players (the Pinnacle, for example). It is the cover that has changed to make the former hot ball now playable. Also, spin characteristics have changed to make it more playbable.
So in the past 20 years, many new courses have been built, and others renovated, to correspond to the increased length. Restricting the ball by 8% would obsolete many back tees. And we'd all be moving up one tee box, I guess.
But, as they say, is "the horse already out of the barn?" Maybe so.
It reminds me of the long-putter rule. I support that new proposed rule, but I wish it had been done many years ago. But, unfortunately, none of us--including the golf rulesmakers--has a crystal ball. I fault them less than others might, because I think they do the best they can with the information they have at the time.
That's why I'd like to withhold an opinion till we see what the R&A experiment shows.
Is that enough of a "cop-out"?