MakerBot Print is our newest print-prepration software, which supports native CAD files and STL assemblies,
allows you to interact with all your printers via the Cloud, and many other exciting new features.
check out http://www.thingiverse.com/make:38748http://www.thingiverse.com/mak..., looks like it worked for him. Not sure where the CG would end up at 15% fill, but you can always add weight if needed. The CG should be at or (<10mm) foreward of mid-wing, if the plane acts erraticly it is probably because the CG is too far aft, making it unstable.