Nice bike. I just sold my Sam Hillborne frameset because it wasn't getting used and needed the money for another project. They are great, solid riding bikes that are incredibly versatile.

I don't totally trust waterproof bags because every one I've ever had eventually leaks a little. What I did with my sam was use a small Rivendell Saddlesack on the back, with ziplock bags for dry stuff on the rear and a Nitto M12 rack with a small Rivendell Trunksack on the front to hold tools, food, tubes, ect....this setup worked well when I used to commute. That small saddlesack could hold a change of clothes and laptop, but the medium size might be a bit better (with a rear rack.)