I wonder how the person who started this thread is doing and whether there is any progress. He hasn't posted here for some time. The Bitwise Ion compiler seems similar in concept. I wonder how hard it is to port that to the Pi.
Use the built-in 100 Mbit Ethernet or force the gigabit dongle to use 100 Mbit mode. The theoretical 3x speed gain with gigabit connected through USB2 requires working flow control and doesn't happen when simultaneously using USB storage anyway.
This thread guides someone through a similar configuration. The person who started that thread has agreed to post a summary, but for now it should be possible to read through the entire thread for guidance.