Copying Over NFS Connection to SunOS

I'm trying to transition from OS 9 to OS X in a pre-press environment. The problem I'm facing is copying large files from my OS X workstation (an old B/W G3) to a RIP station running SunOS 5.5.
Previously the workstations connected via Appleshare served on the Sun box by Xinet X-AShare. Trying to connect using afp:/... produced Appleshare errors, so I'm trying to find another way to mount the file system.
I tried using Samba, but it was painfully slow. I tried connecting using NFS Manager, but I had problems transferring files. I decided to try the simplest way I could think of to connect via NFS:

sudo mount -t nfs -w [sun box]:/home/user /[local mount point]

It mounted, and my test file transfer (a 240 MB Photoshop file) went over pretty quickly. However, there were some significant problems. To illustrate, here are some Perfmeter screen shots from the Sun box:

Old method, using OS 9 and Xinet:
http://homepage.mac.com/bypung/OS9_Xinet_240MB_copy.jpg

New method, using OS X and mounting from the command line:
http://homepage.mac.com/bypung/OSX_NFS_240MB_copy.jpg

About two-thirds of the way through the transfer, the G3 froze for a while, but everything went back to normal. When the file finished transferring, however, the G3 slowed to a crawl and the Sun's disk access went through the roof. Why it is doing this is a mystery to me. I was finally able to convince the G3 to stop the transfer.
Any help would be greatly appreciated, either troubleshooting this method or suggesting an alternate setup that may work better.