KINGDOM HEARTS!!!!!!!!!!!?

i am having trouble beating clayton on proud mode in kh1. i have already defeated the whole game on normal difficulty. i can get through the first part just fine, when u hit clayton a few good times. then the invisible lizard thing comes out and thats where i have trouble. i figured out that if u stand on the edge of this little ledge thing, clayton cant shoot u or hit u at all. but as soon as i jump down from the ledge, i start attacking him and the first time he hits me i die even though i had full health gauge. i tried guarding the attacks but i still end up dying. any help?