This might give you some tips.I have not used it personally but have also been looking around since I will be putting up my first this year also!! It should at least help with ideas. I will be going 20 feet high for my floor though at least and may possibly go with 4 of the smaller sized telephone poles for my bases.

Link: http://www-personal.umich.edu/~jeffreym/htm/Elevated%20Deer%20Shack.htm