I want to export midsurface model to STEP file.

Solid bodies are hidden in shell configuration, but I get STEP model which contain both: hidden solid and midsurface

Of course I can delete (not hide) body in shell configuration but in this case I loose all mates in my assembly in shell configuration

Iges works good for one part, but for shell assembly I get the same situation.

Is there a way to export only surface. It is possible to use other format.