I like the light rails a lot more than the hydrofarm movers. I've always ended up having to dick w/ the slip clutch on the hydrofarm units, and there's no travel adjustment.

Go down to Casa de Pot and have a look at the replacement hardware for sliding screen doors- those trolley sets will slip right onto your rail. Space 1 per 18" of flexx duct. You don't have a lot of weight, so you can use the single wheel trolleys and put them on the side of the rail that doesn't have the travel stops.

If your hood has the duct fittings in line w/ the bulb, and it's six inch, I've seen folks run aircraft cable right thru the duct and hood, fixed at each end. Must be braided steel or other temp resistant material- hemp twine isn't gonna work. You just have to install a mount point at each end- long bolt( also casa de pot) thru flange fitting works well. Drill flange for bolt, use 3 nut on bolt (head/flange/nut on one end, nut/flange/nut on the other to keep flange in round. You'll want to use another se of nuts to prevent cable from slipping. Run @ highest points w/ muy tension- prop need a barrel adjuster. Let run for a while w/ bulb turned off to make sure that your getting clearance off of the bulb- six inch flanges should leave enough room. CDP will also have " starter flanges" that you can mount onto your fan, if you don't want to mod the fan and moving duct must be attached to it.

In a pinch, you can run a shower curtain rod ( or 3/4" pvc pipe) paralell to the rail, and use those shower curtain rings w/ the barrell bearings- yer duct will pull a little offside, but nothing to cause a problem.

Hope this helps.