A designer that is currently moving from Rio de Janeiro to Perth, Australia, Roberto Barros has some interesting designs to examine. Mostly sail craft, but a few power boats.
Designs are available in "ply-glass, steel or aluminum". Most of the power yachts have a "sailboat" hull look to them (fairly beamy). Mr. Barros has some interesting interior designs, again seeming to borrow from some of the sailing designs. Getting berths for 6 in a 28′ boat sounds tight, but by stacking them "bunk" style with the uppers designed to fold to become seat backs, it seems that he has managed it. Check out the pictures for more details.
Note that this web site didn’t work correctly for me in Firefox.