Monitor shielding? How can I avoid interference from another monitor?

[Crazy Cooter]

Refering to this thread:
http://forum.arcadecontrols.com/index.php?topic=39027.0

I'm looking at taking a Nintendo VS dual machine and changing out one side.  It looks as though I'll run into a problem where:
"The problem is that both monitors are mounted so close to each other that the yokes 'beat' together at different frequencies (although ever so slight) to cause a roll bar in the picture do to the differences in sync frequency between the two different boards. This was never a problem in the original games' dual system configuration since both games were originally run from one single main board so the both monitors received the same exact sync frequencies."

Is there a way to shield the two monitors so that the 'beat' is not an issue?

[Ken Layton]

Yes, heavy lead or copper sheeting with ground wires attached to the sheeting and to earth ground in the cabinet's wiring harness.