Special functionality has also been added specifically for the designers of Americas Cup class yachts. This is enabled only for purchasers of ACRule which can be accessed by entering an authorisation code in the Options dialog in the Windows | About Maxsurf dialog.

In the case of Americas Cup class yachts the constraint applying to LWL has been replaced by one applying to the AC LBG value, a length measured 200mm above the DWL. In addition, the Parametric Transformation automatically constrains the forward and aft girths to the minimum allowable value, as measured by a chain girth at the forward and aft girth stations.