The stop point stays the same, it's a point on a chart that you feel indicates a bonafide reversal. That part does not change. You just don't add so many positions that the point on the chart would lose more than 2 percent of total liquid net worth.
Wasn't he way overextended? I don't believe having a stop placement that loses 2 percent or less of total liquid net worth would be overextended. Furthermore, he was trading back months which are very illiquid. Also, I generally am not using more than 1 to 1 leverage .
But your stop SIZE does. Therefore the amount you lose on the stopout changes as you postion size changes.
If you are not using the leverage in ES, then why even trade it ? You would be better off trading spy and not have to roll over or pay higher commisions.