Ubuntu will not be able to use U: if you formatted it with NTFS. You may as well just erase U: and leave it as empty space. Ubuntu will find it and ask you if you want to install side by side.
Also, make sure you backup you Windows just in case something gets FUBAR.
When you install Windows as the second OS it WILL attempt to take control of the bootloader; with Ubuntu being installed second you should have no worries.
The glass is neither half-full nor half-empty; it's merely twice as big as it needs to be.