For comparison purposes it may be a good idea to duplicate the surfaces prior to modification (the duplicate surfaces can be made to lie exactly on top of the originals by specifying zero for all three spacings). The duplicate surfaces should then be made invisible so that they are not affected by the transformation. If, after the transformation, you make the original surfaces visible, you will have a direct comparison of changes to the waterlines, buttocks and sections.

Tip: by holding the mouse cursor over the contour lines you can see the surface name and the contour line name in the bottom left of the Maxsurf window. Note that this method of comparison will not work if the model is trimmed as the coincident surfaces will corrupt the trimming information.

Hull comparison after 2% change to Prismatic and 1% change to LCB

Another quick way to compare the hull is by simply doing Ctrl+Z to undo the Parametric Transformation and Ctrl+Y to redo.

It can also be a good idea to make a copy of the hydrostatic data before the parametric transformation into Excel and compare it with the data afterwards.