Greetings Terzaghi,
Your plot is very doable. One word though flags me though: trees.
Trees can be a nightmare. They can cause signals to bounce around, be reflected and ultimately arrive at your antenna much weaker than your TVfool plot calls for.
What kind of trees do you have?
Normally in situations with trees you go with a stronger antenna than what your plot would call for. This is appropriate in this situation. If I were installing an antenna on your roof without knowing anything more than your plot and that you have trees, I would go with an
Antennacraft HBU44.
http://www.antennacraft.com/Antennas/AntennasHBU.html and
http://www.solidsignal.com/pview.asp?p=hbu44. This antenna is recommended due to high-VHF support (real channels 7-13) and UHF (real channels 14 and above).
Mount antenna either on the chimney or via tripod on the roof. Orientate to magnetic heading 233. If you can find a spot where the trees thin a bit at magnetic 233 all the better. I would expect to see ABC, CBS, FOX, MyNet, NBC and PBS from Tulsa with this configuration.
How long will your coax be and how many TVs do you intend to service?
Edit: Go with the 20' elevation if you can. There are telescoping masts made by Rohn. A 30' might be a good choice mounted next to your cabin.
http://www.rohnnet.com/rohn-telescoping-masts