Nice space David!
You're going to cover up two brand new sliders with foam so as to accomodate the screen? Why did you install them there in the first place? Code? Existing openings?
Dave's got a point about condensation, but with new thermal windows, if the foam is sprayed directly on the panes and frames, condensation could never form as there would be no temperature differential (polyurtehane/Icynene has a huge R factor, and is closed cell...no moisture can penetrate). But why? Is it to late to simply remove the windows and close up the cavity? Prohibited by code?
Either way, that's going to be a beautiful theater David!