small TD

Thinking of taking a 4' x 4' trailer I have(Menards bolt together)and stretching it and building a small TD around 6 foot long x 3' tall(too short?). Originally thought of using 1/2 ply for the walls, but have been contemplating sandwich walls, my main question is what thicknesses to use(1/4 ply inside and out with 1x studs?). Would like to go with a scad-about type profile. Here is trailer as it is now
http://www.tnttt.com/gallery/image.php?image_id=23078
Thanks
Aaron
http://www.tnttt.com/gallery/image.php?image_id=23078
Thanks
Aaron