Think of it this way, your performance bond is held by oec during regular market hours. At the 3:15 pm closing the clearinghouse matches trades and determines open equitiy positions for all the clearing fcms. These fcm's then credit and debit respective customers balances and transfers or recieves net funds from the clearinghouse. All trades must be matched and settled at the end of the day per the clearinghouse. This is why even if you sell your position at 3:31 cst upon opening and you are under the performance bond requirements you will recieve a margin call and not be allowed to trade the next day or until you have adequete capital as that bond is posted against the previous day's trades.
I had the same problem with Tradestation, until I called them, and they enabled my account for daytrade margins. Incidentally, they had an additional proviso that a hard stop was necessary (within 7 pts) in order to qualify for the day rate.
The buying power in the display is calculated based on overnight margins. It doesn't restrict you during the day. You'll find that you can trade much more than 8 contracts, irrespective of how much buying power the program says you have. Try it on sim.
I know people who leverage their accounts all the way. Some are inexperienced and blow their accounts. Some use systemized stops and profit targets, and are successful. Depends on the skill level and market behavior.
Is this a real account or sim account? Simulator account uses exchange overnight. Real accounts should calculate using SPAN.