Posted: 15/04/2015 at 08:00
I think it's beautiful as it is
One of the wonderful characteristics of some magnolias is the asymmetry of their growth - that's why they look so wonderful in Japanese gardens and paintings where asymmetry is prized.
If you cut it back you run the danger of it looking like a frilly loo brush.
I'd enjoy it as it is and accentuate the asymmetry and the Japanese style of the garden - perfect with the architecture of your house