OK, Fine.
GSC_InitProgress.extent = "x y";
You must be doing it wrong, or you have strange vertSizing and horizSizing values.
Or you have multiple controls with the name "GSC_InitProgress" including one which is off the canvas, and since you can only address one object by name at a time there's a good chance it's the one you're not trying to alter. Do "GSC_InitProgress.delete();" loads of times until you get errors, then re-create it.
You don't have to "get sassy" with me, I did read your post and what I posted will work just fine provided you haven't done anything stupid and can manage to substitute "gui", "x" and "y" with the appropriate values.