Well, balloons still come in slightly different shapes and orientations. Even if you used my example for one shape, the other balloons might be rotated or shifted slightly, or slightly smaller or larger. You need to try drawing up some different shapes and not just having one balloon shape. For example, in this pic found on Google Image Search:
Even though the top two purple balloons and the dark blue one are about the same, the red and green ones slant left and the yellow one slants right. See what I mean?
