No need to install. Edit /usr/local/etc/fml/main.cf to back the fml_version to the previous one.
Just when the file is saved, fml is changed to the new version.
author's homepage is www.fml.org/home/fukachan/.
Also, visit nuinui's world :) at www.nuinui.net.
For questions about FML, e-mail <fml-bugs@fml.org>.