Check out the 'camper mobile' story on page 7 for a H21 fully loaded complete with sound system! H18s have excellent carrying capacity,speed and can be sailed solo. I don't know if you have 16' Calypso cats in the US. These had large deck hatches which allowed huge in-hull storage and were quite the rage in Oz for camping holidays.

If you want a cat with below deck accommodation look for Seawind 24s/or malcolm tennant designs for sale in your area.

If you want to build your own and have about 3 months free, go to members.optusnet.com.au/~rhturner1
for the Aussie Jarcat trailerable cats.