Hey Nathan, the SG6042 is a wind turbine airfoil. I designed a small DC autogyro recently and used that airfoil on the blades with very good results and was just curious as to why you picked it for a fixed wing a/c. Not saying it's bad choice 'cuz I have no clue about using it in your application.

As far as the CG goes, I think the TVC (tail volume coefficient) would be more important in making your choice than the airfoil section. Check out http://www.aalmps.com/tv.htm for how to calculate the TVC. There's also a nifty free aircraft design file for use in Microsoft Excel here in the aero. forum a few weeks ago. It works great!

Hope this helps ya!