Is it safe to use the MagSafe Duo charger on a metal surface?

I recently got a MagSafe Duo charger, and I'd like to use it on my bedside table, which is made of metal. I've previously used a single MagSafe charger on the table with no problems. However, the Duo sticks to the table like a magnet, whereas the single MagSafe charger doesn't (unless I flip it upside down, so the charging side is touching the metal surface).

The instructions for the Duo say, somewhat vaguely, "Place your MagSafe Duo Charger face up . . . on a flat surface, clear of any metal objects or other foreign material." Does that rule out a metal table? I thought it might, but someone asked a similar question about a MagSafe charger that stuck to a metal table, and the answer was that it was probably OK. Is there a definitive answer?