It was true - Doug was new to the game and Stephanie's right hook resembled a freight train, but he'd been diligently practicing for well over a month. "I kind of let you hit me that one time. At least, I was going to, but realized I was going to have to roll with it or you would have broken my jaw." He winked at her. Perhaps saying that would make her less worried about hurting him.
Falling back into defensive stance, Doug watched her body movement. He had two advantages in order to do as Batgirl said... his height and weight and strength were the first part. Granted, Steph was probably stronger than she looked, so he wasn't going to get cocky.
The second part was his read of body language. It made it easy to predict where a person was going to be, once he understood their own physical 'accent'. To restrain her was going to require locking her joints, and wasn't going to be easy as simply striking back.
Doug gestured with his outstretched hand, eyes locked on her every movement. "Go for it."