Thanks to those who tried to help me get a pathetic old Celeron 400 optimized to run freenet acceptably well.
I caved and spent the time to build freenet for OSX (With native jbigi libaries!!!) using the current stable source. I knew just enough programming to make the few code changes to support loading the jbigi library for OSX and managed to compile jbigi.jnilib using the I2P source and insert it into the freenet.ext.jar file. Then I stuck that into the freenet source directory so that I could then compile freenet using ant. That may be nothing to the the developers that hang about here, but I'm damn pleased ;-)