It kind of depends on what, "significant rocker" means. If the rocker makes the waterline a lot shorter there is less boat in the water to support the weight therefore you may have reduced freeboard somewhat.
In the end kayaks are supposed to sit fairly low in the water to make them less effected by winds and waves. I suppose "how low, low is" depends on what you are comfortable with. If you upward thusting stems are not catching the wind and trying to stear you and water isn't getting into your cockpit you should be OK.
To the best of my knowledge the books say 6" minimum for canoes but not a word about kayaks.

: So some of the messages in Kudzu's thread about paddler weight got me
: thinking... what is a good freeboard general rule (if there is one)?

: I've been paddling my slightly modified Nikumi for about 8-10 hours now, and
: I've noticed at the cockpit there is very little freeboard. The boat has a
: significant rocker (at least the way I built it) so my stems are quite a
: bit higher than my cockpit is. I'm quite comfortable in the boat, to the
: point where I can literally lay back on the deck flat and continue
: paddling, but if I rest my arms down on the gunwhales, my elbows are
: literally in the water.

: The boat is incredibly stable, even in some fair chop (6 inches to about 10
: inches) and she paddles great, but I have a lot more freeboard, even in my
: greenland inspired NorthBay.

: So the question is, what's the general comfort rule for designs? Obviously
: every individual person is going to have a different comfort level, but
: I'm looking for general design rules. I would suspect 2-3 inches is the
: norm, and that may be what the Nikumi has, when unmodified, but I have no
: more than an inch or so at the cockpit with varying levels at the bow and
: stern.

: Any one have any ideas?

: FrankP