I am putting together a Sig Somethin Extra. I am at the point of mounting an Os46fx and I have run into snag. Being the first time of building an arf, I don't know the correct way to mount the engine to the mounting arms. I have the arms on the firewall, but I don't know if they are correct. If I put them on one way, the engine sits high. If I turn them over the engine sits lower in the fuselage. Which way is correct for these plastic(I think) mounts? The second question is about placement of the engine on the arms. From what I've read, the spinner backplate should be about 1/8 to 1/4 inch in front of the nose of the plane. However, if the engine is placed all the way to the rear of the arms, the engine (spinner backplate) still appears to be to far out in front of the nose. Third question- how do I actually attach the engine to the arms? I know the engine has 2 flanges with holes, but do I drill through the arms with a drill bit and then put some certain size bolt with washer on top and a matching nut on the bottom of the arm? I can't tell if the flanges have threads in them. And last if the firewall has the correct thrust angle built into it, how can I be sure that when I put the engine on the mounting arms that it will be the same as the firewall angle? Thanks.