Zooming each layer is about the only way to do it... I had to do it like that with Chamber. The problem I am having is that the game runs by default in 4:3 ratio, and if I try to make it adjust the window size to something other than a 4:3 during runtime, it won't do it.
I am more than happy to post a cut down cap file of chamber if you guys want, so you can see how I did the resolution thing, but it only works in 4:3 aspects.
~Sol