I don't know what's so wrong with this set. If you look at the pics of the studio model http://www.modelermagic.com/?p=1781, you can see that the bottom side is nearly flat. maybe in a small angle, but by far not as pointed as your moc.
For example compare http://4.bp.blogspot.com/-c1jTRJN3fsA/TfvPnjyEIGI/AAAAAAAABoQ/IX__NkiUSIY/s1600/10221_1.jpg and http://www.modelermagic.com/wordpress/wp-content/uploads/2009/01/kg-ssd-executor-reference-036.jpg with http://www.brickshelf.com/gallery/Anio/SeTechnic/Executor-UCS-ST05/a08.jpg.
I would even say that the official model's bottom is more accurate than your's.
