Well, just so you know, there apparently are SPF checking systems out there using that first IP in the header.  Your setting stopped me from getting SPF rejections from @weg.com addresses at the very least, and if one major company is using SPF checking software that uses the header IP, I'd be willing to bet there are others..  

Also the appmaildev.com SPF test uses it (which is what led me on the search for how to change the originating IP):

But seriously, thank you for your response and help!