My proposition is

1. remove trading range at all or
2. provide clear rules for "additional clearings" which change the trading range so users can calculate the risk

If you do additional clearings arbitrarily you effectively change the trading range at will. Many people have margin calls that they wouldn't have if additional clearing was not done because spot price dip was short lasting. In effect they feel that arbitrarily done clearing "margin called" their accounts. No clear rules for additional clearings justifies their feelings.