Very interesting thread. One of the fish I've read that should be off limits for most ponds due to overpopulating.
Didn't catch how big your pond is....but here is one more idea to kick around. What if you used a feeder or just hand fed the fish in a specific spot at a specific time every day. After a month or so of this when the green sunfish become used to it place a large net on the bottom under the spot you are feeding them from. As they group up to feed net what you can and then sort through the catch, throwing back everything but the greens. Then take a week's break of not netting them but still feeding them to fool more into the next netting.
That, combined with some extensive "catch and pitch" rod fishing (maggots below a bobber would be a good choice) might be enough to put some serious hurt on them. Combine that with the above advice of stocking more gills and/or adding more large bass might help greatly.
Oh, and if you don't care to net them go pick up some H1000 firecrackers and just pitch one into the feeding school every so often. :')
You could also throw in some flathead catfish but then that brings up a bigger problem. :') Reminds me of the one Simpson's episode where they planned to let snakes go in the city to eat some invasive lizzards. "Then how do we get rid of the snakes?" "We release some snake eating apes." "Then what do you do about the apes?" "That's the beauty of it, when winter comes they'll all freeze to death."
