长期点数图 (long term point and figure charts)

Have you ever heard the expression that less is more? This is true in many cases but especially in forex. I have found a very profitable long term strategy using point and figure charts. Here are the rules for the system.

Buy at one box above the starting point of the first box in a downtrend
Sell at one box below the starting point of the first box in an uptrend.
A trend is defined as 10 or more boxes in the same direction.
Stop loss is when you get a signal in the opposite direction. Alternatively stop loss could be placed near support or resistance on a candlestick chart
Use the system on EUR/USD

Example
Sell at the red horizontal line which is one box below the starting point of the first box in the current uptrend.
http://img27.imageshack.us/img27/878/unavngivetaqz.jpg

Take profit when you are satisfied with your profit. Don't be greedy.
http://img27.imageshack.us/img27/29/unavngivetr.jpg

What do you think about this strategy? I don't have the exact figures but I think it is profitable in about 90 % of the trades. the problem is when to take a profit. I don't have exact rules for that. The indicator I use is attached in this post.

Edit: Before you ask any questions please read all the posts in the thread. I don't like repeating myself again and again.