JCIFS WAN performance vs. Windows

I'm working on a project which is using JCIFS to copy a single 40 MB file 
across a WAN with 70ms latency. The server is a NetApp Filer. I've tweaked 
about every parameter I can, but I can't get above 4 Mbps on Linux, 
whereas using a simple copy command on a Windows 2008R2 client I'm seeing 
30 Mbps. Both are using SMB 1.0. I've upped the MPX count and snd_buf_size 
to match Windows.

Linux command line:
/usr/local/java/jdk_8u5_x64/bin/java -classpath ./jcifs_1.3.17/jcifs-
1.3.17.jar:. -Djcifs.smb.client.snd_buf_size=33028 -
Djcifs.smb.client.maxMpxCount=50 -Djcifs.util.loglevel=3 -
Djcifs.resolveOrder=DNS -Djcifs.smb.client.dfs.disabled=true TestJavaCopy 

Graphs:
JCIFS:
http://i.imgur.com/Zl386qK.png

Native 2008R2 client using "copy \\UNCPATH <localdir>:":
http://i.imgur.com/MIFcr39.png

Any thoughts?  Packet details available upon request.

Thanks,
Mark