Sorry for the late response. I can't remember all the values I tried, but I was reading up on some other threads that mentioned the same thing and didn't have much success.
Here is some of the values I remember.
copy_nonbufferio_threshold at 0 and at 1.
copy_buffer_size: 64kb, 5GB, 15GB, 50GB
I also tried this forum, which is a good work around.
I decided to just manually open up windows explorer each time I wanted to move large files or use the solution from the link above.
I am using FlexRaid on Windows Home Server 2011. I also tested it on windows 7 with FlexRaid and just windows 7 alone, but I had the same result, even without FlexRaid. I think Directory Opus just caps at 50 mb/s over the network. After I changed the settings a bit, it ended up going to the 60's, but that still low compared to what I get with explorer.