The left fork tube is longer than the right. The only way to get it to center would be to file the tube axle rest. I do agree that letting go of the handle bars is not a wise idea.Perhaps you can make the fork work with some creative cold-"bending" in all the right places so that the wheel, when "dropped" into the upside-down fork, sits so that the rim is centered up by the crown? I have found almost any bent or poorly-spec'd fork can be made right with some work. And if that doesn't work, dish the wheel to better center it at the crown. But, a disclaimer is necessary here......the bike will not track true with your hands off the bars...