Capping Clipped Models in a Volumetric Window

I'm currently developing an application where the models present inside a volumetric window may exceed the clipping boundaries of the window. ( Which I currently understand to be a maximum of 2m )

Because of this, as models move through the clipping boundaries, the interior of the models becomes visible. If possible, I'd like to cap these interiors with a solid fill so as to make them more visually appealing.

However, as far as I can tell, I'm quite limited in how I might be able to achieve this when using RealityKit on VisionOS.

Some approaches I've seen to accomplish similar effects seem to use multiple passes of model geometries rendering into stencil buffers and using that to inform whether or not a cap should be drawn. However, afiact, if I have opted into using a RealityView and RealityKit, I don't have the level of control over my render pipeline such that I can render ModelEntities and also have multiple rendering passes over the set of contained entities to render into a stencil buffer that I then provide to a separate set of "capping planes" ( how I currently imagine I might accomplish this effect ).

Alternatively ( due to the nature of the models I'm using ) I considered using a height map to construct an approximation of a surface cap, but how I might use a shader to construct a height map of rendered entities seems similarly difficult using the VisionOS RealityView pipeline. It is not obvious to me how I could use a ShaderGraphMaterial to render to an arbitrary image buffer that I might then pass to other functions to use as an input; ShaderGraphMaterial seems biased to the fact that all image inputs and outputs are either literal files or the actual rendered buffer.

Would anyone out there have already created an effect like this that might have some advice? Or, potentially correct any misunderstandings I have with regards to accessing the Metal pipeline for RealityView or using ShaderGraphMaterial to construct a height map?