On a straight left lead, parry to the inside position with the right hand, and then drive a right hand to his chin. As he jabs, lean to the left, slightly, raising the right forearm inside his left and forcing it outside. Step forward and to the left with the left foot, shifting weight to left leg while raising right elbow to line with his chin, keeping left hand up to guard and drop a right hook on his chin. Start slow as you coordinate the moves; I never got it right but it’s possible. I read that Ezzard Charles used the move.
On a straight left lead, cross-parry with left glove and drive right hand to the heart. This move seem risky but remember that you know what's coming and he doesn't so, if done properly , you open up a whole platter full of opportunity.
Let me add here a couple right hand counters after slipping that I forgot above. FIRST as he leads a jab quickly turn the body to the left bringing the right shoulder to the center line. From here drive the right hand into full extension; a short step to the left, then shifting the weight over a straight left leg will add power. SECOND as he jabs step forward and sideways with the left foot. Shift your weight to the left foot, turning the right hip and shoulder through to the center line. This will allow his left to slip over your right shoulder as you drive your right arm to complete extension and to the heart.