It's usually not a good idea to sell the first sharp downwards swing, regardless of the pattern. It's rare for a top to be an inverted V-shape. Instead, wait for the upwards response wave and judge its strength. If it's moderately strong, you can wait to see the strength of the next down wave. If it's very strong, hold; if it's weak, sell into it. If the rebound wave doesn't come within an expected time frame, definitely get out and consider going short.
A lot has to do with how each wave reponds to the previous one. Traders can get taken out easily in the scallop pattern, but if they'd waited for the response, they'd be sittin' pretty.
@HOLIDAY1 -- yes it's all a mind game. Psychology is critical.
