6 @ 7 seconds, would be around chest high, maybe some bigger shoulder high peaks.
I would call 6 @ 12 to be solid head high, with some 1-3' OH sets.
Also, remember, it depends on the break. For example a reef break in Puerto Rico will go bigger on the long period swells than most breaks on the east coast for the same swell. The longer the period, the more variability you will see between different breaks due to the refraction process as the swell feels the bottom further off the coast. The short period swells are going to more peaky and overall weaker.
Last edited by Swellinfo; Jun 7, 2009 at 01:38 PM.