The only restrictions are around the ammo jetty inside Cockburn sound. Well that's last time I was out that way in the boat, which would be the same for kiting I think. It's fun testing them out though, we had them come up in a high powered boat with guns last year. Some sepo aircraft carrier was in at port.
IMO You would be taking a large risk doing a downwinder through these area's. For starters from penguin island through to garden island, Carnac island and stragglers there is scattered reef everywhere. If something goes wrong you will have difficulties getting into any beaches along that stretch with a prevailing SWer.
If you did make it you would probably come through the gap between garden island and Carnac or keep going past Carnac and come in. The cockburn sound isn't that nice to finish up so you would have to keep going down wind to Woodies to finish. That's a huge journey from start to finish.
I have a suggestion which is safer. I'll be doing down winders in summer from madora to secret harbour. I'm also going to do some longer ones from madora to safety bay. I'd love to arrange to meet up with anyone interested and get a group together which would be safer than by myself obviously. Google earth it and let me know if you intersted.
Later