Importing a Snapshot from a window off screen

[Ray]

Greetings - Has anybody had any success importing a snapshot from a 
stack's window which is offscreen?

I'm looping through every card in a stack to import a snapshot using 
something like:

    import snapshot from rect myRect of window myWinId

This causes a lot of annoying screen flicker so I'd like to place the 
stack's window off screen, do the importing and then return it on 
screen.  But doing so gives me blank images for the snapshots.

Any suggestions?

Thanks!