the tension on the left side will be as low as 50% of the right side with the Power-tap hub.
As you increase tension work on radial true, making the wheel round. It is possible to have perfect tension and still be out of round. On 8, 9, and 10-speed rear wheels the non drive side spokes will need to have about 60 percent as much tension as the drive side to center the rim (dish).
Be sure to stress relieve the wheel as the tension gets close.