I used the lightrail 3.5's for a few years. They're cool, ( currently have them in storage,) You can adjust the speed of the motor, and they have kits if you want to run multiple hoods. They run very quiet. For a display tank, I don't personally like the look of a bulky track/ moving lights above my display , but they're cool for long frag tanks.
Might be cool for an LPS/ Softie tank. For a stacked SPS tank Id prob go with a standalone fixture. With the LR 3.5, the rail, the motor housing and the eye bolt for the fixture account for roughly 5-6" vertical space down from the mounting point. Would need an extra tall canopy if enclosed in a hood
Look at wet thumb frags, they use them and sell the too! I think Mr Salt Water TV has an episode on youtube at wet thumbs. Facility that shows them in use.
[FONT="]MattL22 you can get on at lightrail3.com and their customer service is awesome they can help you find the lightrail you need with the adjustable time delay you can decide how fast the motor moves your light. [/FONT]