Well, transparent like blender renders are.. just the object with a semi-transparent shadow and see-through windows (visor in this case). So i can make my own background behind it (and you can see a bit through the visor and stuff..).
now i realized whats the problem with your render. See the refraction. Your glass IOR is too high so the cage and everything looks bigger than it suppose to be. Check refraction settings.
The seat is from XRR and I needed to scale it down due the unit differences and some shit. Maybe I should have scaled it down a bit more. The glass material may not be right but it's not the glass making things bigger than they are.
You seem very sure. All I know that I've sometimes used glass material with IOR number 1.6 getting results with bending light. IOR 1.0 fixed this. Maybe you can enlighten me someday but not here.
I had almost the same problem,
look at the headlights
this was the solution:
If you have modeled as a glass-sided 1 level, the template geomtery use thin glass, and is the glass modeled as a mass (with thickness so) than the template glass - use solid geometry.