Building a hog bipe just now and in the instructions it says that the fuse doublers areprefabricated so that when you glue the firewall in the notches provided then 1 degree down thrust is achieved. Think the astro hog may well be the same.

Well scrap what I said above I just looked at a astro hog build and I see to my suprise it is a totally diferent build.

Im sure if you build to sigs recomendation you will get a good flying plane and if the instructions or plan dont call for thrust angles then they prob are not needed.