The idea is right...but you should backtest the chart to make sure the vertical distances on the channel width keeps hitting BBT,BTT,BTB,TBB,TBT AND TTB (TOP, TOP, BOTTOM). I have used this method for a long time and it's very accurate when the channel "post vertical" is correct. There are often 2 to 3 channel sizes that run at the same time. ie. large, medium, small.