mrboywonder wrote an answer about Kona King Kahuna on December 17, 2011
I'm 6' with a 32" inseam.
I threw my leg over (but didn't ride) a Kahuna Deluxe (same geo, lower component spec) locally after seeing these on huck n roll. They only had an 18" which I thought would feel too cramped, but it actually felt really good. I'd say go with the 18"