In discussing this design with Jack last year, I believe he suggested that the snow loads for this building might need to be checked against current codes. I'll ask him tomorrow when he comes to the shop, if I remember.

Cutting a 4' brace is the same as a 3', you just have to calculate the hypotenuse.

I've cut 3-4-5 braces. Layout is with the square. I like to leave the degrees out of the thought process. They are also easy to layout and cut.