I'm inclined to agree with Matt. If you have soft spots in the sides of the hull, then you've lost a great deal of strength there. I'm willing to bet the hull is less than 50% of its intended stiffness and could easily break in half.
I definately would excersize extreme caution sailing the boat in this condition.
You might consider a major repair which would probably result in the hull being stronger-than-new if you're up for it. We performed this on my friend's Sunfish with a big crack in the keel.
1) Remove the soft spot so you have a large hole in the hull
2) Get a piece of oak board and cut / sand so that it fits inside the hull with contours to ensure maximum contact
3) smear flox/epoxy on inside of hull and oak board
4) Insert epoxy-slathered oak board into hull and pull tight
5) Allow to cure
6) Fiberglass over remaining hole
7) Repaint hull
See part three on my Sunfish page for images and more narration: