I trade futures so I'm not well versed on the topic of equity day trading. I have heard of traders using 4:1 margin when they are deemed to be "pattern day traders". Is this so they can trade 100% of their cash each day and not have an issue with the T +3 day settlement rule? So a trader with $100k cash would have $400k day trading buying power - he could day trade with $100k each day without a margin/settlement issue? Thanks.