Cob: Realistic sized homes

[Neana]

I have been doing a lot of surfing, reading, etc. and building a home 
with cob calls to my soul.  Unfortunately, it will be some time before my 
soul can get time to answer.  :(

On the other hand, this leaves lots of time for dreaming and envisioning. 
 The many beautiful pictures of cob homes that I have seen are definitely 
cottages and I appreciate the reasoning behind creating a small home.  
However, I have two teenagers, pets, lots of 'stuff' and hobbies.  The 
house I am imagining currently is basically round with a 36 foot 
diameter.  It would peak at about 20 feet tall and slope to about 10 feet 
on one side and 15 on the other.  I realize this is generously sized.  My 
question: "Is it unreasonably generous?".  It would be approximately 1500 
sq feet when the large loft is added.

Is that even do-able in a season?  Not finishing the interior.  Just the 
walls and roof.  I am in SEKansas, the summers are long and hot.  The 
winters are cold and messy.  The RF factors suggested for this area would 
be easily reached with a wall that started at 20-24 inches thick and 
tapered to about 18.  

Thanks,
Jee
PS if you see any gross mistakes in these assumptions, please let me know 
gently.  ;)