Now i am doubting you are who you claim to be------ there is no such thing as a symmetrical moving average. Symetrical means taking data from both before and after to create an average... but obviously with market data you don't know what the future data points will be. So WTF are you talking about? peace surf
There is such a thing as a symmetrical moving average - you just defined it. Formally, if it's time T in the past, and we want a 100 wide interval for our moving average, we take the average of the periods T-50 to T+50. Obviously you can't use such a thing when building a trading system.... or when you backtest it will have forward data and look amazing. However we're not building a trading strategy here. We're just applying a filter to past price data to adjust it, so we can then run our backtest on it.