Just get yourself some of the plastic flexible dryer ducting. Connect one end to your light, the other to your exhaust fan or the solid ducting leading to it, and then support it in the middle with some twine or something that will swing back and forth as the light mover goes.

If your exhaust is set in the middle of the light mover's travel you just need the ability to absorb 3' of movement on either side, which the flexible ducting should be able to handle without any trouble.

The air cooled fixtures are a scam. They don't accomplish anything that can't be accomplished better with a different method, and turn about 10% of the light instantly into heat. Eventually the light that makes it through the glass barrier will also turn into heat, which is why the air around the plants also needs to be cooled,
either with air conditioners or external ventilation.

With your 400w hps magnetic ballast, you could run a 400w ceramic metal halide (CMH), note that is NOT a regular metal halide. The CMH produces a full spectrum and is about 50% more efficient than hps.

The hps is not compatible with high frequency digital ballasts and low frequency digital ballasts, and that includes all digital ballasts except JBP (which costs twice as much and few besides my friends know of it).

They are lying or stupid when they say hps will work on digital ballasts typically found in growshops. The hps bulb is designed for 60 hertz, and high frequency digital ballasts will cause acoustic resonance, leading to premature failure of the bulb and leaking mercury unto the plant. See the hortilux article in october 2008 issue of maximum yield magazine (available online).

That doesn't make any sense. An air cooled reflector doesn't turn light into heat any more or any less than a normal reflector. Any time a photon hits something it transfers some of it's energy in the form of heat. Shiny surfaces absorb less heat than dark ones, etc, but no mirror is perfect. Glass absorbs some energy, air absorbs some energy, EVERYTHING absorbs some energy from the light emitted until eventually it's all absorbed in some form.

Energy, like matter, cannot be created or destroyed. So if you put a light in a closed box and none of it's energy were absorbed you could turn it on and then off and there'd still be light inside.

The bulb puts out X amount of energy regardless of what kind of fixture it's in. The only question is how much reaches the plants. A reflector of some kind improves this.

By using an air-cooled fixture you remove waste heat more effectively. You're not significantly impacting the amount of useful light that reaches your plants, and you're massively reducing the distance your HID's have to be from your plants to avoid cooking them.

It doesn't take a rocket scientist to figure out that if you can put your lights twice as close without harming the plants a little drop in light output is moot.

Air-cooled hoods have a glass bottom, which instantly turns about 10% of the light into heat. Better to postpone the conversion into heat, so plants have a better chance to absorb light energy. Eventually light turns into heat, and life turns into death, but what happens before then does count.

A 360 degree rapid spinner (a type of light mover) cools the bulb much more than a fan, because of increased air movement past the bulb.