While gamma scalping itself was a subject of discussion few times already, my concern is the potential profit vs. margin. My margin calculation in example below, selling call ATM option and buying delta # shares of underlying goes as follows: 1. Margin for uncovered portion of call (typically 30% of underlying`s value) plus 2. Margin for long stock position (typically 50% for marginable stocks). Adding above together gives quite high number, so it would not be easy make significant return on capital. Is this calculation right ? Can anybody share some experience regarding this issue ? Any opinions greatly appreciated.