Hi CS1!
if i understand right, its all sheetlayers...
so if i have this problem i duplicate the whole sheetlayer rename it let's say "A3 transparent".
set the pagesetup than on this sheetlayer and than using the allign and distribute tool. place the top and bottom viewport, activate all viewports and run distribute space vertically and "align to the right", for example
sometimes i use a 2d locus to mark the printed area and group it with the viewport, so i align to the loci if my viewport is located in the middle of the page...
hope it helps somehow...
cheers