In 3 visits and 7 total plays on the two courses, I've always found 2 Red/16 Black to be the most frustrating. There's no problem issue if the pin is on the right/front of the green, but that left/back plateau is a bit too small and a bit too high for my taste. In subsequent plays, 6 Red/12 Black has moved up right next to it because it's just a bit too shallow/narrow given the typical firmness of the greens. I'm also not a fan of the left side of the green on 6 Black because again, it's too shallow and too tough to get pin high right to have a relatively easy putt. But I like it as the back half of the 12th green on the Red because you should be able to hit your pitch straight enough to leave the straight putt from the front of the green.
I also think that 5 Red/13 Black is one of the better greens on the course but the issue with it is that although it's deep from both directions, you're almost always playing a long shot into it. And because almost the whole thing is convex, it's very tough to hold.
I have no complaints about the 18th green. Many do their best work early in a process...before they start over-thinking things (not that I'm accusing you of that here!). In fact, I find 9 and 18 to be about the two least-questionable greens on the course, if not my favorites.
Brett, you are not alone in questioning 2R/16B and 6B/12B.
I was unsure about 2R/16B at first, but have come to find it very playable and fun. If I miss the green (often), I found I can chip to any pin with a shot in the air or on the ground, with a varied degree of risk depending on where the pin is. But I've chipped it close many times and holed at least one for birdie that I recall.
On 6B when the pin is up on the left plateau, I found it's foolhardy to approach it directly, you have to hit it left of the pin, where there's a flattish spot that is more receptive. You might be off the green, but it's a straightforward putt from there, and better than being long or short. Also note 6B often plays downwind in the summer, and even those of us with modest length can be right in front in two.
A low-handicap friend of mine on his first visit summarized 6B/12B green with a comment that "It has a short par 5 and a short par 4 playing into it, and the green seems right." I agree.
You've hit on one of the issues I have with 13B/5R. The par 3 13th is a 200+ yd uphill shot playing into a green that you can't see and that slopes decidedly away from you, and the green has a lot of roly-poly contours and the convexity you mentioned. Getting the ball on or near the green, with a reasonable crack at an up-n-down is a matter of luck, not skill or precision. Coming at it from the Red direction, at least you can see the green, but I agree it's difficult to hold with a long approach, typical for most of us. One redeeming feature about 5R, when the pin is way back left, there's a small backstop that you can use in fun ways to get your third shot close.
The green at #9, despite serving 2 holes, has only one approach angle that makes sense for me, from the left side. Then the front greenside bunker gathers rolling balls like a black hole, and the green slopes off to the left on the left side, so there's a very small slot to roll a ball on. These are a 400 yd+ par 4 and a 575yd par 5 that often play downwind in the summer. Recently I was playing with a guest who was seeing the par 5 for the 2nd or 3rd time and without any comment from me as we were standing on the par 5 9R tee, he said "this is a really severe green for this hole."
On the other hand I watched a high-school kid play 9B, and all he did was fearlessly hit a mid-iron sky high and land it softly on the green, presto. He 3-putted though.
Tom,
I think the green at 18B works great for the short par 4, but I have had some frustrating moments on 18R--which again is an uphill shot to a complex target that you can't see. It and 13B share a feature at the front of the green I call an "ice cream scoop" because they are partial false fronts remind me of the concave shape you get when you dig in a scoop on a brand new package of ice cream. They repel balls away from your intended line, or if you're putting or chipping towards them, they bring out a dread fear of watching the ball roll past the hole and off the green. I have learned to play away from that feature of 18R but can't always accomplish what I want. However, after many plays I finally birdied 18R, so my opinion of it has improved measurably