Here is a simple floor plan that can be adapted easily.
This one is a steel SIPS home that typically will score a HERS 58. My 1466 sq. ft. homes I built hear in New Orleans all electric have a $960.00 annual electric bill with only $260.00 per year for the heating and cooling, the best value is in investing in a solar water heater (30%) of the total energy use.
I and my homeowners loved the floor plan.
http://structall.com/residential/content/images/floorplans/amelia.pdf
I always took the kitchen wall out to make it one large room the living room has a 15' high cathedral ceiling the MBR has an 15' high Vaulted ceiling and the back bedrooms 14' vaulted ceilins and drop ceiling over the hall and bath area provided 150 sq. ft. +- of climate controlled attic with vaulted ceilings there as well.
It is the Amelia and displayed as a two-story on the cover and two more of my models including the Sanibel which are both Net Zero now with a 3 KW system.
[embed]http://issuu.com/structall/docs/residential_catalog?e=8589257/3614701[/embed]
The Celebration here is a unit similar in design dimensions (note the Garage became a 400 sq. ft. bonus room or mother in law apartment is some adaptations).
http://structall.com/residential/content/images/floorplans/celebration.pdf
As far as your overhang question even with a truss roof wind uplift is a concern because you are building an aircraft wing in essence.
I can send you more information as well as provide ideas for adapting the BOX as the interior layout does not affect the cost to any degree it is the envelope is what matters.
I worked for the company for the four years as well as actually constructing 15 in my area and actually doing the work while the other guy does the talking in the installation sequence.
General note the width of the hall batch should be 5' from stud to stud as this is the width of standard bathtub I find that 5X8 is a very efficient design.
If you really want to have some fun try Cheif Architect it allows you to create post-it notes and slid them together click a button and it will create a complete floor plan for you to insert doors windows etc.
https://www.chiefarchitect.com/home-designer-DIY/
Meanwhile, I can be reached at
[email protected] Good luck,
Eddie,
Sr. RESCOM Project Manager (Ret.)