If you have the original owner's manual, it should show a graving dock diagram which gives you this information. Some boats will also have a marker on the side of the boat where each sling goes. On convertibles, the rear sling seems to usually go under the main aft bulkhead, forward of the shaft log entry point- obviously you don't want the sling anywhere near the running gear. The front sling would go at the convexity of the hull where it isn't going to slip forwards when the boat begins to come out of the water.
I haven't seen a 53MY hauled in a while, but my recollection is that it takes four slings to pick one up. I think they weigh about 80K pounds, but that's just a guess. You might want to send a PM to MikeP or SkyCheney- they may have photos of their boats being hauled which will be some help.
Sam's may have a copy of the graving dock diagram; if not, Hatteras Yachts may have it.
A yard that is getting ready to haul a boat that large and heavy needs to know what they are doing. If they don't, have them learn on someone else's boat, not yours.I think you would need a 50 ton lift to be safe.