How to make composite prop spawners?

Composite as in I weld several props together and then make a spawner out of that.
I have AdvDupe 1 and 2 and Wiremod installed.
Usually you’d just copy the stuff you want to make a spawner for with Right-click in AdvDupe2 and then hit R to make a spawner. However in case with composite props the resulting spawner itself can’t be copied and pasted properly, which means I will not be able to save whatever contraption I want to use it in. When I copy and paste such spawner, either the pasted spawner does not spawn the entire original composite prop, only a part of it, or it spawns it entirely, but at the moment of spawning the prop just flies away with great force. Either way it’s unusable.
Any ideas?