How does SOX do in cold weather conditions? I know SOX is similar to fluorescent lamps and they have a rough time in the cold. my home brew fixture is currently in service above the outside door and I'm curious how it'll perform in a Michigan winter.

I'm not sure about this, but the man who would know is James, fire off a PM to him asking about it. 

The LPS are similar to fluorescents in being low pressure, but they still run way hotter.
Plus unlike the fluorescents, the major way the arctube looses heat is thermal radiation, way less influenced by the colder side temperature (heat transfer is proportional to T^4), so I would not expect any issue once the lamp has ignited.
However igniting it at cold could be completely different story. Many LPS are just marginal regarding their ignition (a bit of internal cleanup affecting the Penning mixture and the lamp refuses to start), so I would expect some problems mainly with the peak ignition voltage requirement vs what the ballast is actually able to deliver.

Fluorescents have problems due to both effects: Hard to start and then too cold to reach full brightness. But at least the LPS arctubes are clean in a vacuum, so they don't suffer from the external dirt and moisture.

So something to increase the starting temperature, like an incandescent bulb might help to raise it until ignition is achieved then switch it off. 

So something to increase the starting temperature, like an incandescent bulb might help to raise it until ignition is achieved then switch it off. 

Indeed, it may help it. Even by another effect: Providing excitation light for some photo emission, lowering the breakdown voltage by having there more free electrons available in the arctube.
But using an higher ignition voltage ignitor or ballast is usually the method of choice, as it does not need to mess with extra socket and lamp.
Plus it will take quite some time to warm up the LPS arctube through the all the thermal insulation it has around when using just an external heat source...

T'was but an idea.

T'was but an idea.

And Iwas caught on it to elaborate what I expect to happen...

I don’t know lol you’ll have to ask someone from Flagstaff,AZ

I don’t know lol you’ll have to ask someone from Flagstaff,AZ

Is Flagstaff really that cold? I didn't got tat impression when being there the few times I was traveling around: November and it was around 25degC (2003 if I remember the year well; then I was in that area in the September and then August a few years later).