Vintage Double Hose

I have two styles of duckbills. three origianal USD and a two repro.

I was trying out the various configurations and permutations of parts to see which ones would give me optimal breathing characteristics.

Has anyone found a difference in the exhalation effort required between the New repro duckbills vs the old style USd ones. I have found one allows easier exhalation than the other, but it is not a tremendous difference. So your feedback is important gents and ladies.

Not totally sure, there are bound to be others with more experience here.
My best two regulators have the NOS duckbills and NOS silicone mushroom valves. They definitly breath easier than those equipped with the reproducton neoprene valves and repro duckbill BUT, I want to add that the difference is not huge, just slightly noticeable that you know it is a real effect and then forgotten about. No big deal. I suspect the biggest difference is the silicone valves because just blowing out of several duckbills I found little difference. If they get stuck they don't do well for sure. I also suspect the thin NOS types may be the culprit in the two reversed duckbill incidents I have seen now.
Here is something I have also noticed, the silicone valves will leak when I roll my shoulder deep to the left and the neoprene repros do not. Slightly annoying sometimes but again, I am willing to put up with that for the better breathing. I notice Dan no longer shows them on his site, could be they are all gone?
James

I feel a slight difference but very minimal. James is right about the original Bec Du Canard being easy to invert. This part is just my observation....After the dive when you are draining the hoses and stretch them out or milk them to get all the water out it sometimes pulls a good vacum and inverts the duckbill. This does not seem to happen with the reproductions as they are thicker.

I don't always run a mushroom valve on the intake side and have been known to run without them all together.....Then again, hose floods are a bit more of a challenge!