Your disk could not be partitioned - Windows 10

I cannot get past the "Your disk could not be partitioned" error. I have tried to work within Disk Utility to discover any errors. I even used Disk Utility from Safe Boot and it seemed to fix something. I have tried the /sbin/fsck -fy technique without luck.

I was on Microsoft support yesterday and they were able to get me an ISO of Windows 10 that I want to install on my 27" Late 2013 with Fusion drive that has 854.5GB of free space. 16 GB RAM. Running El Cap 10.11.4.

I have a USB stick with the Boot Camp tools and the ISO in the external CD drive.

I saw another post to try to make a 1TB Windows partition. Is that the solution? I really have no desire to burn 1TB on this :-(.

I also saw another solution to back up to TM, erase HD, and restore from TM.

Any ideas?