I’m curious what issue you are currently experiencing? I run catch cans on high performance marine engines but that is simply because such engines have more blow by than most along with intercoolers that would loose efficiency if coated in oil. But in a 4.0, unless the vent system on you valve cover isn’t working properly (which is a serious possibility), I’ve almost never seen a single drop of oil in that tube.
Kind of ironic too that we used to dip air filters in motor oil to improve the filtration of fine particles and prevent the top ends from rusting prematurely