Chris,
Thanks for the hint. I was thinking of a 'step down' tube of some sort, but that should work as well. Just fyi, the operations manual says to 'blow down' the lubricator with risdual steam at the end of the run. This works well if you remember, also it depends on having a place to blow the old water/oil onto the roadbed without making a mess of things. All in all, I prefer the manual extraction of the grunge with a syringe.
Joel