Possible to create collision-less NavMesh helpers using solid frames?

[Briljasen]

I (think) I know about externally imported things like plots and navmesh helpers needing to punch through whatever NavMesh might exist underneath it to actually provide viable pathing in game. (Am I right about that btw?)

Would it be possible to create "solid" frames (i.e. cube with a single negative cubic hole in it, for clarity) with collision that do the punching, having a thin wafer of NavMesh on top, in the same manner you would frame any sheet of something?

I'm having problems getting attackers to fall into my traps and the vanilla trapdoor is garbage.

The idea is that the frame will be enough collision to break the native NavMesh enabling the bare workshop-placed NavMesh mounted on it to exist without problem and AI will step into my trap chasm like Wile E. Coyote.

 

[Modhunter]

Most of the normal walls/floors will provide that for you. You can box in the area around the top of the trap as well as the bottom.
A new piece of Navmesh will not make any 'Holes' in existing Navmesh, it will just be another chunk of Navmesh added to what is there.
The only way to make a Hole would be to Edit the original Vanilla Navmesh, which is a BAD IDEA for a number of reasons, mostly game stability.