ORD Terrain workflow / guidance for iTwin

Hi

I would like some guidance on how best to process terrain models in ORD (2022 R2) to allow them to be synced in iTwin.

I have been doing some testing and I can't quite achieve what I want.  I only want to see the terrain boundary in iTwin in plan view, and when I create a cross section I want the terrain surface to be displayed, but without the need for the terrain to be displayed (in plan).  I am saving the terrain models as dgn and syncing with the civil connector and using iTwin (connect).

I've seen it done on another project but I can't seem to replicate this.

Could anyone provide any guidance on display symbology or process, please?

Thanks