Hello,
Maybe you can check with Dan Berger danberger@mindspring.com in Virginia Beach for a used side rail. I'm sure he'll have one on hand, as he is always buying and selling 14s and 16s.
Good luck,
Jack Hoying
Fort Loramie, Ohio
Prindle 18 #1645
http://www.bright.net/~jmhoying/sailing/prindle.htm