Relative to the size of some engineering document package I've had to monitor, vessel data sheets minuscule, if your talking about the U1-A forms. IMO evertyhing on them needs to verified.
The contractors probably have you weding through ever piece of paper they genererate (data sheets, outline drawings, specifications, etc.) before they send them out for bid. Then you're probably in a bid review loop. After the contract/PO has been issued you probably get to look at every fabrication drawing the comes out of the supplier's door. Let me know if your asking about what parts of all those documents you should focus on. I'll elaborate if that's the case.
Otherwise, the true vessel code data sheets are small potatoes and should be completely reviewed without too much trouble.