the depth in that picture comes from the repetition of rafters. keep in mind that the timber rafters are not flat, they're 3-d. you'll feel that width and meat on the timber when you cut it with an edge tool. it may want to form a crown at the heart of the tree, for example. just something to be sensitive to in your ideas for the outcome.

both of those are very pleasant tools to procure. anywhere from a yardsale to lee valley to our friend Jim here.