Schilke 5a4 vs 6a4a

[VintageFTW]

What are the major differences between these two mouthpieces? I'm referring to the vintage designs, as opposed to the modern ones. I know that obviously the ID is smaller and the backbore is bigger, but other than that, how do they compare? The reason is because I need a replacement for the original Jet Tone BC that was on loan to me until recently and I have the opportunity to get a vintage 5a4 on the cheap. I know that ideally a vintage 6a4a would be a good choice, but unless any of you people have one on hand you are willing to sell I can't find any.
How much smaller does the 5a4 feel though? How does the resistance compare? How about comparison of the sheer power output?
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1880's Thompson & Odell Boston
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1903 L&H "Improved Own Make"
Early 1900's Marceau Cornet *B&F Stencil
1922 Holton-Clarke Cornet
1954 Elkhart built by Buescher 37b
...And many more

[RonWilson]

I would go with the 6a4a FWIW

[MF Fan]

I've played the old Jettone BC and it's nothing like the 6a4a. I'm playing a Steve Patrick BS5, which is patterned off the Jettone 5B, which is supposedly the same basic mouthpiece as the Jettone BC. I suggest reaching out to Steve for advice. He is very familiar with the old Jettone line and will likely be able to get you what you need.

Edit: Found this link for the mouthpiece you're looking for on Steve's site:

http://patrickmouthpieces.com/mouthpiece-models/#!/The-PBC-Piccolo/p/11796561/category=2605565
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