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The small plane (http://www.thingiverse.com/thing:1983683) if about 15g and levitate really well.
The bigger plane (http://www.thingiverse.com/thing:1980197) is about 30g and levitate but is quite unstable.
If you make a bigger coil and/or put more amps in it, you could probably levitate more, but don't expect to levitate a real car ;-) !!