These things are not tooo expensive, except maybe the shipping, however as Ken notes once installed they will hold any ten plus SeaCrafts tied together. All you need is the 6" anchor, any larger they really can be difficult to install by hand. In the power/phone business they are installed by hydraulic powered equipment on heavy trucks.
http://www.linemen-tools.com/No_Wren...h-j6526wca.htm