Well the radius to the outside of the bend is 2" so that gives a total circumference of 12.56". Since each bend is only a 90 degree bend, you take a 1/4 of the total circumference which comes out to 3.14".
Now as far as the straight length of the port wall, I came up with 10 1/8" and about 3 1/2" after the bend in the back. Now I've heard that you measure the length of the port to the midpoint of the kerf flare. I already factored that into the design, but I doubt it would change the tuning too drastically.