-The best roof is a flat roof. (because it's spacially economical, and it's all that is necessary to keep the weather out.)
-The best ceiling is a 7 ft. ceiling (6ft. is too low, and 8ft. is unnessarily high)
-The best overall dimensions are 8ft. by 8ft. by 9ft. because this size can be carried, lying down, on the back of :
- Any truck, any time, anywhere in North America, and yields an inside measurement of 6ft. by 6ft. by 7ft.

  For an 8ft. by 8ft. by 9ft. structure:

  Each module occupies 4 cu. ft. and there are 4 tetrahedra in each module.
  Therefore each tetrahedron represents one cubic foot of the 3-D tessellation.

 Subtract the number of modules necessary for a door, 3 wndows, and a chimney (10 modules):

81-10 = 71 modules