Andy, Mo is the second poster on this thread. I was agreeing with his comments.

If you are using 8x8 post make the tie beams 8x10's not 6x8's. You mentioned purlins, I don't see any common purlins in your sketchup. The purlin plate on top of the queen posts could be sized to 8x8's, as well as the tie between the queens. The joist are a bit small for the 11' span. As this is a model you can utilize full length stock with no problem, 56' top plates etc.

What scale would you be using?

Tim