Yeah, 1.3.023 seems pretty clear (for the UCI) in the rule book, especially with figure "structure (1b)".
No higher than the top of the saddle, no further back than the steering axis, no lower than 10cm below the top of the wheels, and no further forward than 75cm.
One important thing, though, is if you have extensions on for a kilo or 500, your saddle must be 5cm back or further.
http://uci.ch/mm/Document/News/Rules...EN_English.pdf