If you change your cash account to a margin account you would not have to worry about T+3 (settlement). You don't even have to use margin in order to have a margin account. But it allows you to use unsettled funds for trading while a cash account doesn't. But one thing you need to know with a margin account is that if you have under 25k in your account they track your daytrading and you can't day trade four or more times in five business days. If you do and your account is under 25k they will put a restriction on your account. If you are a pattern daytrader and have over 25k you don't need to worry about anything.