Might want to rethink your run layout and it's roof.
Snow load could be a serious issue....a flat mesh roof, especially one that large is susceptible to collapse without sturdy framing support.
Sounds like you'll need a center beam supported by posts to support the rafters.
Which would be advisable anyway at 16' is a pretty long span for a single length of lumber.
Are you going flat across....or....?
Some pics might help here.
Oh, and.... Welcome to BYC! @cheldi
Where in this world...