It's like ever since Layer to Slice routing came out, people forgot that layers have a size and position as well.
Here's a super simple setup (made in Avenue even) for a Triplehead, that has layers to position content on the left, middle, right projector, as well as over all of them.
I started doing it this way but decided to start using layer to slice to save layers due to limited archtitecture of my midi controllers. I already put myself into a corner cause im workin' with the 3Head and at least 2 to 3 projectors.
So i always have a emulated native screen of 2560x800 or 3840x800.
I always build the layers up like this:
Layer8: Layer for laser emulation
Layer7: FX Clips for Foreground Layer5 getting input from layer5 routed to duplicated slices on top of layer5's
Layer6: FX Clips for Foreground Layer4 getting input from layer4 routed to duplicated slices on top of layer4's
Layer5: Foreground Clips2 1280x800 routed to different slices all over the 2560x800 / 3840x800 output Mapping
also used for 3d Obejcts in the way of light
Layer4: Foreground Clips1 1280x800 routed to different slices all over the 2560x800 / 3840x800 output Mapping also used for 3d Obejcts in the way of light
Layer3: FX2 Clips for Backround Layer (Blocks&other Stuff) getting input from layer1 routed to duplicated slices on top of layer1's
Layer2: FX1 Clips for Backround Layer (Strippers&Mirrors) getting input from layer1 routed to duplicated slices on top of layer1's
Layer1: Backround clips 1280x800 routed to different slices all over the 2560x800 / 3840x800 output Mapping