Here’s a very sound swing by a powerful guy that could be jacked up to produce freakish distance and dialed down for control by freeing it up in the backswing with wider turn produced by greater overall trunk movement, initiated by a wider move with the upper body and an almost immediate deepening of the right hip. In order to feel this wider takeaway (more “carry” with both arms) I would first have him soften his arms at address to look more like “home plate” (elbows bent) than like the proverbial “triangle”. By concentrating on rotating his spine and including all the muscles in the back, sides and chest he could gain close to 6 inches of carry, or extension, away from the ball, which can be marked by noting the space produced between the end of the grip and the edge of the right thigh when the shaft is parallel to the ground in the backswing. As this is happening there needs to be a conscious effort to move the right leg backward, with the right hip going up on the angle of the pelvic tilt and the left hip tilting downward. There will be a feeling of loading into the ground by pressing the right heel downward, but as the leg moves back the knee will actually lose a few degrees of flex. As you load the leg into the ground and pull it back it may not feel like there is a straightening of the leg, but you should not emphasize maintaining all the flex. This combination at the beginning of the swing should allow the upper right arm to free up from its present position where it is tethered to the body, and will produce a higher and deeper position at the top. Considering how strong Matthew is I would think this could only produce more power, while the control could come by refining “knockdown” technique where the swing is essentially the same but cut off in the backswing and the follow through along with gripping down and inch on the club.