The magnet method Austin420 mentioned would probably be ya best best, leaves it adjustable then.
The super strong magnets are the "Neodymium" type or rare earth magnets is another name for em.
You can find them at radioshack and stores like that or bust open half dozen old computer hard drives, they have them in them too.
A bit of experimenting will determine how many magnets you'll need, also just when you think you have enough, add one or two more to be safe. Last thing you want is the power board and lights letting go and squashing ya plants!
I wouldn't recommended duct tape as when it warms up, the sticky stuff will go all gooey and drop off.
Hope that helps ya dude
