OK Paul, yesterday I took my Newell for a run. I took it to a wash rack that has a significant incline and hung the rear of the coach over the peak of the incline so I had some room under the rear of the coach.
When you can get the light up under the rear of the coach, there are two large tubes just dumping down into the air. These are located one on each side of the engine about 4" to the rear of the starting point of the mesh under-engine screen.
This photo was taken on the passengers side of the engine. The starter motor gear is directly beside the slobber tube.
As I haven't cleaned this area in the two years and 27,000 miles I have owned the coach, it is not a major source of oil but it is significant enough that now I have a new project. It isn't the easiest place to get to with the screen under the engine but I have now added this to my list of things to do.
So, in addition to the airbox drain canister, it looks like we do need to add a way to trap the oil coming from the two large slobber tubes.