The latest Rhino 8 WIP provides for creating reflected parallel projection viewports. This is done by changing the projection for a viewport or detail to “Parallel Reflected” in the properties panel.
The lower left viewport in the following image is a Top view with TestReflectedViewport applied.
This should work in both regular Rhino viewports as well as detail views.
Please give it a try and let us know if this is what you want. Thanks!