Snowman, I also am 6' 4" and have a bad knee so I try to not bend my knee too much. What works for me is to make sure to release the ball at the "flat spot" at the bottom of my swing. Releasing early drives the ball into the lane close to, or behind the foul line. Releasing late launches the ball on an upward arc with a resulting lout "thud" and a poor shot. A release in the flat spot allows the ball to glide onto the lane, much like an airplane landing. Yes, it may touch down a bit further down lane than used to be taught, but it works pretty well. The flat spot can be described as that point at the bottom of the swing when the arm is perpendicular to the approach, with the ball (ideally) just at your heel.
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