Well, based on you folks' experience, I stopped by Lee Valley today and picked up 10 rare earth magnets. I just went with the 1/2" diameter and even then I am worried they might be too strong!
I am just using some gorilla glue to attach them to the top of the eggcrate screens. It says that I should clamp them when glueing, and I didn't, so I guess we will see how it goes....
- Chad