Dane,
I mostly fish from shore but using a kayak to get to waters where big GTs frequent is something that I've been pondering. If you are targeting GT in the 5 kg range, I believe that would provide for great kayak game. However, I have not bought a kayak for GT fishing because of a few reasons. For one, I know that it would be difficult to cast and work normal GT lures effectively while sitting on a kayak. Secondly, unless in deep water, I am not sure if stopping big GT from running and cutting the line on the reef is feasible when fishing from a kayak.
Fishing for GT in Okinawa is something that interests me as well because I often visit the island. I have been to Kerama on a charter targeting GT but would like to learn about where GT can be found in waters closer to the main island... Well besides at the aquarium in Churaaumi
. Guys at a fishing shop referred me to a captain who takes GT fishermen to waters more easily accessible than Kerama but I have not made it back to try my luck out with that particular captain.
That being said, I have seen places that potentially could be big GT hunting grounds off Okinawa's main island which you could easily reach by kayak. You could probably also catch GT from shore at some of those spots. Personally, I wouldn't be comfortable fishing in those places on a kayak unless I were intimately familiar with those waters and the ocean conditions though.
Let me know if you find anything else out. Okinawa is the one place that I'd rather live than where I do live. Fishing is an essential part of my life so it'd help me to get a bit of a head start if I ever move there.
Ken