don't know about m. alba but i have pruned my m. figo into the shape you describe and it has responded well. i took off lower branches up to about 4' and have not had to cut back the top. don't see why you could not do that but this usually stimulates the shrub to produce more lateral growth near the area that was cut.
my shrub is older than yours and is about 15' tall.

From what I've heard, M. alba doesn't get over 20-25' outside the tropics, so your local climate may keep your tree at the right size for you, particularly as conditions change at roof level. If you need to prune, don't remove too much at once, michelias, aside from the shrubby ones like M. figo, don't take well to hard pruning. Spring is the usual time to prune magnolias, but check with local growers to see what they think.

Enjoy the blooms!

Jim

Thanks for the inputs.

I live in San Francisco, Ca. I have a michelia albra tree growing in my backyard for almost 30 years and it is about 30 feet tall and each year it blooms a lot of very fragrant flowers. My tree is so tall that I can not cut the top branches at all. As I heard that the michelia alba tree can not stand pruning or cutting to much at one time. If you want to cut, do it on Oct or Nov.