Here is a reply from my friend who owns a couple pair of Green Mountain speakers and knew Roy well. He is very technical, basically an engineer:
I've found over the years that people don't want advice in audio forums.
I'm staying clear of them all.
People used to argue with Roy, who was a Physicist, about speaker design.
None of them ever won the argument, but some kept trying.
Tell them anything and you're an audio snob.
Between you and me, I doubt any "updated" drivers would work, as Roy used 1st order crossovers in all his designs, meaning the woofer had to play higher and the tweeter lower.
Those drivers are not easy to find.