Mr. Daley,
My first impression about the bunkering done at RMGC, KH, and the Met club is that all the faces were constructed from the original ground coutours, hence, the sand, soil and peat had been in place and compacted for several thousand years. Like Mr. Goldie said, the sandbelt sands compact very well. I know that at Talking Stick, any soil that was moved to make bunkers, tees, greens, mounds, etc., had to be water because the soil would not compact without it. There were always water trucks on site. It would act as pure sand. If I were to construct bunkers in this manner today, I would go about placing a 3-5 inch ring of stacked sod around the general outline the intended bunker.(The soil profile would be directly under it.) Therefore, there would be a stable edge that would not crumble and would always allow for grass to stay tight on the edge. With this sod in place, an edge would always be easy to cut because soil will not fall apart like sand. Plus, by the time the course were to open for play, the sand would be pulled up enough on the faces that the black soil would appear as if it were pure sand.
Bunker comparisons in the US would definatly include Riveria, Talking Stick, Bel-Air. An a smaller level-Pasatiempo, SFGC and Valley of Montecito