I haven't fished with corkies in a while, but when I did I would try to make sure that the hook was large enough so that the hook was larger than the corkie. That is, the distance between the hook point and the shank was just a tad larger than the diameter of the corkie. This is to ensure the fish still gets a hook point when it grabs the corkie. I think I usually used a size 2 octopus hook and size 10 corkies.