Well it is true. Double lots= double profit (double lose). But i think it is better way which is quite similar. Don't use double lots- instead of using 2 lots we will use 1 lot but we will open 2 position at the sam time and in the same direction. Put take profit only on one of those positions- second one close manually but above TP. if price is going in good direction- put SL in entry point. You won't lose