I've also seen some Panama Canal scenery with AI ships moving back and forth.
If you remember where you have seen such a traffic, I would be extremely interested. Panama Canal sceneries I saw up to know are not flat. So it would not be possible to create an Afcad for this area. it's the same problem as f.i. for the Mississippi River. Leaving New Orleans
it works up to Baton Rouge, but not further north.

I made the experience that the parking area in the Afcad should be a "Dock" and have at least a radius of 600 ft. Don't ask me why!

On of the longest traffic I made goes through the hole lenght of the Sognefjorden in Norway. For my last traffic I let me inspired by the said japanese video and added to stops for two Staten Island Ferries. It works perfectly.