This is a 1x2 stacker with a pass through side to allow it to be very dense with multiple belts.
Notes:
- Perpendicular input port is stacked on top.
- In/out ports away from the perpendicular input port is a pass-through.
- It's made for big assemblies of many space belts.
- I used belts instead of launchers where possible to maximize legibility, so not blueprint point optimized.