D 0.5 sounds about right for a glazed bulb, but you can play with textures (semi transparent) and light colour too...

I find it easier to import the model to SH3D and re-export after having set the correct dimensions (this depends very much on the model software used). With rotation and dimensions present, I guesstimate the x, y, z co-ordinates for the light. Obviously, if you have the correct (absolutish) values in Blender, you can also use Blender to measure exactly.

I forgot to mention (in the SVG guide) that you can add several light sources to one object. More about that in the repositories, as you appear to be more than able to figure it out on your own [:)] - good luck, and it would be fun to see the result.

ok