Octygon roof problems

[dparsley]

Am getting ready to build new deck with octagon roof over it. Have drawn it with concave roof and it looks fine but when I show framing in 3-d or just framing, the hips are not generating right. see pictures. Another question is what is the right way to calculate hips for octygon roofs? i know regular hips are usually figured on 45 degree, which in my case is 16-12 for the common rafters and 16-17(17 the run on the framing square) for the regular hip at a 45 degree angle, I will have hips at 22.5 degree angles?? I have built these before and would normally set the commons and then measure the long point to where I would be cutting the birds mouth over the top of the cornner with same amout left in the rafter as is left in above the birds mouth on the common rafter. does anybody know what the "run" would be for figuring this hip???? Hope I made my self clear enough. All help would be appreciated