Timberwrestler,
Thanks for taking the time to review my proposal.
Tie Beams- I realize that 8x8 is a bit light but "assumed" having 4 ties with wedged half dovetail joints and collar ties on the principal rafters to reduce spreading force would be adequate. I'll go to 8x10 for a little extra margin.
Rafters- You're clearly right on this. Looks like either heavier and/or more rafters.
Metal roof- 2x4 purlins on 2' centers makes a lot of sense, guess I'm having trouble with the look from the inside.
Carl