Wes,
Sounds like fun! I've worked with Architects in the past helping with design problems and might be able to help you as well. I own a small TF company north of you in Ferndale, WA. Visit our website to see the 12 sided tower I designed the frame for. It had a 14:12 cone shaped roof with a 4:12 slice through it creating an eliptical ring in which all 12 rafters joined the ring at different compound angles. With an octagon, I think you would probably be looking to use a boss pin in the middle with rafters hitting on each face and possibly struts down to the bottom of the Boss pin? Check out our website and give us a call if you'd like to discuss it.
www.twodogtimberworks.com Pete
