I have just copied the code from the manual and tested it in a C++ app and in LiteC with some entities created with ent_create.

In 7.10 it works, the event is called and when I return 1 the mesh is not rendered by the engine. In 7.50 the event is called and dispite returning 1 the mesh is still rendered by the engine.

I have also noticed that models with no texture (even if it was assigned a material effect in MED) will not render. This didn't happen in 7.10.