And the answer is 100% The code references are: 230.42, 215.2, 210.19
The issue is "continuous load". Since residential loads are not considered to be continuous you can load a branch circit, feeder or Service to it's actual rating which is 100%. I don't think it's a good idea but the code allows it. Most inspectors would recommend a little head room and most contractors agree and provide this head room.
