I've not tried it, and it should work OK but there is one little catch. The idea of using two center channels, one above and one below the screen, is that the two centers produce a "phantom" image that's locked in the center of the screen, which is a consideration with large 120-inch front-projector installations.
If you use two centers on each side of the TV display, there is a possibility that for viewers sitting off-axis to one side or the other, the dialog will move to the center speaker nearest the viewer, in the same way that if you just listen in stereo and sit to one side, the soundstage shifts to your side to the speaker nearest you.
With a large display, and centers to each side, the shift of dialog to one side of the screen might be perceptible and off-putting.
Incidentally, magnetic radiation from a speaker affects only Cathode-Ray Tube (CRT) displays. LCD, Plasma, DILA, and DLP displays are immune to any sort of magnetic radiation.
Axiom Resident Expert