Cree XP-L V6 2C led, tested against XM-L2 T6 3C, edit23/7: I repeated the test and measured a dedomed XP-L

Flashlight Modding and DIY Parts
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#3 may be a better candidate than you think. DBCstm has observed that the dome does not appear to attach to the die. According to him there is actually a pocket of gas above the die!

EDIT:
Post #135 in the "Cree XP-L, XM-L performance in an XP size package" thread.