If you would like to see the finished inside instructable please click here ...http://www.instructables.com/id/How-to-finish-the-inside-of-a-12-x-20-cabin-on-a-b/
Step 1: Floor Illustration
Step 2: Drilling and planting the posts
2nd pic * shows the post planted and the bottom 2x10 Stringers.
3rd & 4th pic* Shows the upper 2x10 x 12 and the 2x10x16 upper stringers being nailed in at 7 foot 8 inches.