No pictures yet but I installed a ladder on the transom of my M15 very easily.  The secret is to install a 4'' opening port on the vertical portion of the stbb. aft seat riser near the transom.  This allows easy access to the transom for installing nuts and washers.  The transom was a solid layup, no core.
 
Ken Abrahams, M15, Petite Fleur, Lake Charles, La.