Is it possible to open and perhaps even edit projects that were created with version 4.0.3 using version 3.5.5? What problems will this cause? thanks

Hello mcah,
 
  Yes, it is possible to do that. Now what's the consequences :
 
RZI files are based on xml and are ascii files. The loader (of IM3.5) will only parse the objects it knows (i.e. the scene objects, materials, locators, and cameras should be read correctly).
The only thing is that "new" database elements that were added in 4.0 (survey points, planar constraints, .. ) will not be imported.
That said if you used constraints to calibrate in IM4 for example, re-calibrating in IM3.5 with the same project will not give the same result.
 
But, I do not recommend to re-save an IM4 file in IM3.5 as you may loose some informations (for the reason said before).
 
Best,
 
Stef

Hi Stef -
 
thanks for the info!