I was messing around with your problem. display smoothness doesn't work when you trim a pieace out. What I did was do extend surfaces. You'll have to play with the settings untill the edge you want to extend. After that when you render it it still looked like crap. What I did was select one object at a time and shortcut press ctrl a and go to the tessellation option. Open that and onther menu opens its advanced tessellation. Check the little white box to turn it on. The settings work how it is know, but you might have to increase the Isoparms both to 4. Heres a pic of what I did.