I found SS to be one of the toughest bosses in the game (only behind D Maleficent and the various forms of Ansem). You said to use the occasional cure but if my memory is correct you don't learn cure until after beating SS. Unless of course you meant potions.
Anyway, because I didn't see this conversation going anywhere I thought I'd share my strategy. First, I suggest that you go with Donald and Goofy as your party members even if Tarzan has a higher level. Next, get a ton of potions and equip them to all of the party members. This will help keep your party members alive and can save you if you don't have time to use a potion yourself. Then, once you get to the fight I like to spam fire against SS. It doesn't do a whole lot of damage but it allows you to attack from a safe distance and avoid being attacked. Then once you run out of MP either use a ether or go ahead and attack him with the keyblade. Finally, once you get SS to a certain health point Clayton will jump off and start shooting at you. IGNORE HIM. Finish SS first. Then focus on Clayton as he should be much easier fighting him alone.
Hope this helps