I have been trying to figure out a good way to do it and here is a rough draft. Let me know what you think! Updated versions will be coming along with the finished product and pictures. Link - Sign in - Google Accounts Let me know if link doesnt work!
I believe that you need to be signed into a a google account in order to see it because it is a google drawing.
Your configuration looks good. How are you going to compensate for the curve of the trunk? As a alternative to Google drawings, you may want to try on-shape.com for drafting. Really decent free Cad software.
What material are you looking to use and I am assuming you will be using plastic washers to keep down the nose from movement?
Using plastic washers is a good idea, I didn't think about that. Thanks. I am probably going to make it out of steel or aluminum. I don't know what camera arms are made out of but I will check.
Aluminum would be lighter but would bend more easily under weight. Possible a lighter gauge steel would be best so it could withstand more.
Your plan seems good. However unless you really want to make one, here's one I'm thinking of ordering from Amazon. Amazon.com : Hunting Game Cam Adjustable Tree Mounting Arm : Sports & Outdoors I don't know if you could make it this cheap either. $30 I don't think you can beat it.
If you do continue with your plan to make one, use aluminum. Steel will be too heavy, and it's not like you'll be standing on it. It's only supporting a fluid head and camera (most of which weigh much less than 10lbs).