Hi actionzen,
The Los Angeles list is in post #2 here. The only one that I know of that uses Mountaintop’s Dunlop Foam is Nest Bedding in North Hollywood but they only use it in the synthetic version of their component latex mattresses and their organic latex models use molded Dunlop. The synthetic and natural versions of Mountaintop latex have a different “feel” because the natural has a higher density and is more “supportive” and resilient and becomes firmer more quickly as you sink into it more deeply than the synthetic. Mountaintop’s 100% natural would be closer to molded Dunlop in the same firmness level than their synthetic latex.
It would probably be fine in terms of ventilation although slats would provide better ventilation yet than plywood with holes drilled in it depending of course on the size and spacing of the holes. A typical slatted bed surface with 1x3" slats (which are actually about .75" x 2.5" when they are finished) with gaps that are about 2.5" apart would have about 50% solid surface area and 50% “space” and holes in plywood would generally have less “space” and a higher percentage of solid surface.
It would certainly be an improvement over a solid surface and would have a lower risk of moisture retention and any mold, mildew, or dust mite issues that can go with restricted airflow in cases where there are other risk factors involved (see post #10 here).
If you do decide to use plywood then I would personally use plywood that was either low VOC or VOC free and I would tend to avoid the use of standard plywood grades because of the glues they use and the possibility of greater exposure to VOC’s (especially formaldehyde) as a result of close contact with the foundation over the course of the night (see here).
Phoenix