Xbox 360 Overheating question.

Right, so... apparently I've been using my 360 wrong. Setting it on carpet could have a chance of it over-heating. So I put a thin piece of cardboard inbetween the 360 and carpet (so the 360 rests on the cardboard; I have it laying down horizontally).

IS this safe? Since my whole house is carpet, I don't have any hard floor to put it on.

It should be safe since the cardboard won't let the 360 sink into the carpet, blocking some vents. But can't you put it on a table?