I built my Constitution under full sail, studding sails included which greatly increases the width by the way. I used 3/16 plexi, Length is 38", width is 21", and height is 32", but 30" will do...outside dimensions. Clearance is about 3/4" on the sides, and ends, she sits on the supplied wood base, and pedestals which lifts it about 1-3/8". I built 2 cases the same sizes to stack them... the other ship required a taller case.
Michael