Ordered File Placement - Not enough room to copy issue (but Pool has heaps)

With the 8TB Archive Drives, I like the Ordered File Placement balancer, fill them up and move to the next.  One issue is that when copying to the pool you get a Not Enough Room to copy a file where:

- The file to copy is larger than the space on the drive being filled even;

- When there is a second empty drive

Eg, I have 7GB free on one drive and 8TB free on another.  When I try to copy a 15GB file to the pool windows fails reporting not enough disk space.  The Ordered File Placement balancer does not seem "smart" enough to move onto the next drive.  This happens both when just trying to copy files to the pool or remove a HDD from the pool.  

Thanks

Nathan