is there anything else I can do to
encourage growth in the lower regions?
Mike,
You could try a technique called air-layering to
rejuvenate your plant. See:
http://tinylink.com/?kdEpDBVZKL
and photos of the process:
http://tinylink.com/?XfhI1pNMO3
Also:
http://tinylink.com/?kco4IWj46V