My only thought on that might be that you could have a situation where the polarities of the strip and small magnet would clash and not let you place the pointer precisely where you would like. Take the small magnet to the store and try it out.

If you live anywhere near a lumberyard or home improvement center, they would likely let you take all the steel strapping you wanted for nothing. Most of the time the yard is littered with the stuff and some poor soul (like me on my summer job as a kid) has to schlep around and pick it up and toss it.