As I sit here at my table;
I see Three 2 litre bottles .Now let's see, How about three? Cut off the narrow end. Using a glue gun, Hot glue the three together side by side forming a triangle. Now create a double bulkhead with spacers, Beads or whatever. Now install engines of your choice. Up front( The original Bottoms.) Create another spaced Bulkhead. Now with the dish of your choice from a take-out dinner, create the front. Sky's the limit here.
So what do you wind up with? a small 1/12,500 Colony ship! The life pods forward contain the crew who Rotate Cryo Sleep till they reach age 40 then they wake the new crew and go into long term cryo themselves. Paint it shades of Primer Grey, Anthracite and Steam Engine black! Oh ! Don't forget to create air locks for the protective fighters and cargo craft( Dropships) on the sides.