If you can find a P16 with rudders that are working and compare them to a NACRA rudder system or Hobie, you'll see instantly the weak points of the old Prindle system.
If you're not worried about one-design class rules, and you have access to other parts, you could adopt a Hobie or NACRA rudder system onto a P16, I suppose.
Rudder issues should not keep you from getting a P16 however. It is a fine boat in many aspects.