Hull Flexing
If it were my boat, I would sail it and not worry too much. While the boats are designed to sit with weight on the keel, if the boat was positioned unevenly on the keel, you could load that area heavier than it should be. This coupled with the boat sitting on the keel for 1-2 yrs. (or more), the hull could take a set and create such a depression. IF you have serious damage, there should be some cracks somewhere and absent these you should be ok. After it is in the water for an extended period, the hull may eventually retake its old shape, but even if it doesn't, the boat will serve you well in any case. If it is serious damage, it will get progressively worst, so just keep an eye on it. If you are crossing oceans where you might be in survival conditions, you might have a concern, but I assume you are not going to do this, and in normal sailing, you should be fine. I helped transport a new 23 ft. trailer sailer from RI to NC on its factory supplied trailer and we experienced some hull deformation at the ends of the trailer support pads in the course of that single trip. I know the history of that boat for about 10 yrs. and there was never a problem. After pulling my previous boat for a bottom job, the marine yard owner, who had been in business for years, commented that my particular boat did not flex its hull when lowered onto the keel and stands like most boats did. So flexing is not unusual and if you put almost anything in a bend long enough, and it will take a permanent set. Also, normal instructions for aligning engine and shaft are that it should be done after boats have been back in the water for several weeks since the distribution of forces on the boat is different than on the hard and the hull flexes to match this distribution. Go sailing and enjoy the boat.
