kedori

I would probably find the lowest and healthiest branch on two main trunks and severely cut the tree back to right above them. This will encourage the trunk to thicken and fresh, new, inner growth will sprout which will make the tree older and far more interesting. I have done this with paper birch, red maple, crab apple, oak, and other trees all successfully. It is still pretty safe to do this now, considering that it is still spring, but don't wait much longer. Good luck!