P3D Upside down twinning

["Jim Harp" <matmail2@xxxxxxxxxxxxx>]

>
Steve Berezin wrote: 
>
>I am working on a twin rig of 2 Canon Rebel Xs's ... I had an idea of making a
>rig that would place one camera upside down cutting over an inch of the
>distance between the lenses...
>
>Both cameras would face the same direction but one would be upside down.
>
>Is there something I may be missing?
 
Won't you get severe retinal rivalry caused by one image being upside down? 
Actually I'm hoping to try the same thing with my twinned Ricoh XR-10Ms.  
Reducing the minimum seperation from 5" to 4" should allow me to get about 2
1/2 feet closer to my subjects, if I understand the 1/30 rule properly. 
Maybe I'll be able to put off getting a single 7P camera for a bit longer
(perhaps even until I can afford one)  The XR-10 doesn't have a pop-up
flash, so I'm considering using the hot shoe to help support the  upside
down camera on the bar.  My plan is to mark the aperture settings on the
bottom of the upside down lense and make the bar short enough to allow
access to the shutter settings.  Also I'll need to elevate the   right-side
up camera by about  3/4" to make the two lenses level.  Has anyone been
successful putting something like  this together?       
Jim Harp