Now, you can provide the additional $6,000 in nonelective (which may result in having to provide additional non-elective contributions to other NHCEs). If his election was to defer only $18,000; then you'd normally need another $35K in employer contributions to get to his $53,000 limit. You can, instead, provide $41,000 in nonelective to get to his overall $59,000 limit (and make $6,000 of the $18,000 deferred become catchup). You'd, then, have to contend with a larger reduction to his "Earned Income" after the additional $6,000 in nonelective plus whatever else is provided to NHCEs in order to pass nondiscrmination.
Call me lame, but doesn't this get you pumped (at least a little) :-) Good Luck!