I'll check around to see if I can find out more on the timing of the two greens. We did look at restoring the upper green, but it's not practical and while it might add 15 yards to the whole (all uphill), the benefit just wouldn't be justified by the costs.
The trees in the 11/12 barranca are interesting. On Opening Day in 1929, Bobby Jones did hit his drive on 11 over that barranca into the 12th fairway, a feat that would be practically impossible today due to the trees. And for safety reasons, it's a good thing the trees are there.
What does happen today, though, is that intelligent golfers who pull their drive on 12 into that barranca often choose to drop on the opposite side of the hazard, in the rough on 11. This gives them a decent shot into the 12th green, particularly if there's a back left pin placement. It's an intelligent use of the rule that permits going to the opposite side of a hazard to drop, since trees in the barranca effectively block any approach shot to the green from the left rough on 12, making that hazard otherwise particularly penal.
Rob