There are default definitiions at /usr/local/etc/fml/defaults/$VERSION/default_config.cf file. Each config.cf of each ML overloads them. Use fmlconf command to show the current value.
% fmlconf $ml_name | grep _dirYou can extract values from config object in a hook.
$_xxx_hook = q{ my $config = $curproc->config(); my $xxxdir = $config->{ some_where_dir }; ... snip ... }
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>.