Once installed backwards the diaphragm will blow out and they become garbage. As you are installing in an RV-dwelling it needs to be of a to stage design which usually means the longer one. 

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of thewestyman
Sent: Saturday, February 14, 2015 2:34 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Propane regulator question

Hi to all,

I have tried three of them and all leak at that little hole.  I have installed them in all direction, but did not help.  
Did I miss anything?
The other kind I can buy is about two inches longer and I would have to cut the copper pipes to fit.  I’m not even sure, I can fit it next to the tank the way it supposed to be installed.  
Who knows of this?
Thanks to any input.
Zoltan