We have the same exact tree, planted partly underneath a huge bur oak. It's been there since at least 1998. It's an aggressive grower & definitely tends to grow toward the light. We've had to prune it significantly over the years to get a more even balanced shape. Otherwise, it would definitely have much of its growth toward one side. It seems to take to the pruning very well.

Based on that, I think I would prune the tree to be more balanced now.

Best wishes,
Randy W.

Thanks.
I'm thinking the same thing. All the pruning guidelines ephasize pruning for shape while young. Too bad, I'll loose about 1/2 the tree -- guess I'll have to do it gradually.