http://www.geocities.com/mec_coleman/18square.htmMichael Coleman's 18 Square Pages.
Beam width isn't restricted, but hull length and sail area is.
If you add a chute, you no longer are class legal within the 18sq rules.
If you lengthen the hulls past 18ft/5m, you no longer are class legal. If you carry more than 18sq meters sail area, you no longer are class legal. This sail area does include the mast area, as I understand it.
Again, refer to Coleman's site, which has a listing of the class rules...
sea ya
tami
