I added another ndf file within an existing Filegroup on another drive.
I allocated about 3 GB as an initial size.
The new file is still not filling up.
No data is going to the new file only to the old file.
The old file has not grown much not sure if this is why it is not filling up the new file.
also adjust as needed auto growth settings for files
read
Round Robin, Proportional Fill and Performance Considerations
http://sqlserver-performance-tuning.net/?p=2552