If you don't know what to hike your silver margin to, just tell your clients cryptically you will hike it to some number (very high if possible) and leave it at that. Best to just leave them guessing.
To NYMEX,NYSELIFFE traders:
Wed May 4 10:50:37 2011 EST
Margin Increase: Silver Derivatives
In light of the recent unprecedented volatility in silver markets, the exchanges that offer trading in silver derivative contracts are increasing the margin requirements on these products. In an effort to adequately address the inherent risk resulting from this volatility, we are increasing margin requirements on silver derivative contracts to a level exceeding that which the exchanges are implementing.
You will be notified as more information becomes available.
Please monitor and manage your risk accordingly.