I would not use the powerhead method myself. Nothing wrong with the riser for allowing the removal of plenum water, {very slowly}, at times. But thats an alternative way and not from the original way Dr. Jaubert published.
Plus I did the course/fine sandbed. If I did one again I would use 4in. of a course media between 3mm to 5mm. This would allow for better water movement through the gravel & plenum. Needs to be deep enough though, with the larger sized grains, so to much oxygen does not penetrate.
Plus I would limit the amount of rock to minimum and elevate what there was. This, of course, is my opinion on running one, as opposed to the plenum systems ran in the 90,s. I have not tested this yet, but others agree with this senario.
The biggest problem is the loss of 6in. of tank space. Of course the sandbed authors figure a plenum is a waste. compared with their dsb ideas. And the bare bottomed aquarists figure both are a waste.
I have seen great tanks with all three. Guess it depends on what one wishes to apply to their situation, and the livestock one wishes to keep.