Thanks Leon, it's all the draw by property settings that I was curious about. It's another one of those things in Mental Ray that is very POORLY documented.

So basically you turn on just about everything, except the one that I have been using (around poly faces) as it seemed to make the most sense. But the downside is you really cannot use that setting on a smoothed model.

I have been looking for a way to get a decent wireframe on a smoothed model and so I will give those settings a try and will have to try to read through the description of all those draw by property settings again to try and wrap my head around how they generate what youa re getting.