"It is experimental, but MAY be implemented in 2004."
HAS been implemented for 2004.
INDIANAPOLIS, IN (June 19, 2003) — The National Federation of State High School Associations (NFHS) Softball Rules Committee adopted the designated player/FLEX rule at its annual meeting June 8-9 in Indianapolis, Indiana.
Go here - http://www.nfhs.org/press/softball_rules_changes03.html
Not mandatory; optional for coaches; but is part of the high school rules next year.
WMB