If you have an account in IB, you can play as much as you want with a paper trading account. It will give you an idea.
you must be kidding. i have a account with ib and also paper trade in ib. what does that got to do with portfolio margin.
Reg T spelled out margin requirements for securities. For stocks it has been 4x intraday, and 2x overnight. Recently the SEC approved portfolio margining that bases the margin requirement on the riskiness of the portfolio (a bit like SPAN for futures). Portfolio margining is optional, and not all brokers have implemented it yet. People are saying it gives you 6x leverage, but that is not absolute. My portfolio usually has better leverage with Reg T. IB's TWS has a button on the Account Management page that estimates what the margin requirement would be if you had elected portfolio margining.
I stand corrected. Our paper trading account mirrors a real one. So, you must have 100K or more and be approved for PM. The demo account (pmdemo/demouser) allows you to play PM games.
check this link out. Maybe it explains what pm is and how to use it in your trading: http://www.philstockworld.com/2007/04/02/portfolio-margin-the-dawn-of-a-new-era/