Will defer to any 0-200 types with experience here. The DD plenums should certainly work. I would include cooling the top of the engine in the plenum. Get a good fit. Helps to think like an air molecule. Also get several sets of eyes on the project. The plenums can be easier than trying to seal the entire cowl area, but must meet normal baffling requirements. Detail detail.
Oil cooling should be done first to see if you are capable of making it work without the updraft cowl flow. Of course no one does the oil cooling first, but rather fabricates magnificent inlets and plenums and then goes through significant agony with superb cylinder cooling but only ten minutes of fright time because of the oil temp. It took me several flights to get adequate oil cooling, and now with a little more work it runs just right around 200 degrees max. Several years ago I had a great vision of how to do the oil cooling better but haven’t slowed down long enough to do the installation.
Last but not least, the DD installations on spam cans are excellent examples to look at for installation detail, oil cooling and carb heat. I developed exhaust augmentation because they all use some kind of low pressure “draw” aft of the cylinders, like a little cowl fence around the nose strut or cowl flaps.
Happy building
