From: 	Caroline Ann Seawright[SMTP:kunoichi@yoyo.cc.monash.edu.au]

Says Takahashi-sensei. It's in the final manga. Happousai drinks the man

drowned water and doesn't change into a young man. (And age does count
in the Jyusenkyou water curse or else you wouldn't have 'Spring of Drowned
Child')<<
Oh, now I remember. This does have interesting implications. Such as the
fact that, even in his 80s, Ranma can be a pretty young girl instead of 
an old hag when he gets wet. I wonder if he would consider that good or 
bad....

Hmmm... although it's probable that your cursed form grows up as you age.
But Pansuto was drowned in a multi-cursed pond as many things died... But
his curse was that of a baby yeti/bull/snake/bird and it grew up as he
did... Hmmm... Maybe being a multi curse messed things up? Or maybe you get
cursed at whatever age you are when you're dumped into a multi-cursed
pond. After all, Ryouga's curse is a piglet when he's not that young...
*shrug*

Kun-chan...