Problems to trust in mass properties tool, solidworks bug!

Dear Solidworks geeks!

I have some problems to trust in mass properties tool.
I need to know the mass CENTER POSITION, because i need to calculate the yacht permforming estability, with that center.
But, in this case, the hull, is mirroed part. In other word, the hull is symetric.
In my case, the models starts with surfaces and ends with a solid model.
The solid model is necessary to know thickness of the hull and see the interference in the assembly of parts. And, know the mass in kg unit.

I think i found some solidworks 2009 bug.

Because, the position demonstrated in mass property tool is wrong, the Z plan is not 0 (zero).
See the image 01, the hull is symetric, but the z position is not zero. (something wrong over here)
I activate de precision calculate in mass property tool, and the same error still there.

Analysing that error i found a bug in shell feature.
1- Mensure the center of mass, using the mass properties tool in the solid hull model. And gave me some units;
2- After i aplicate the shell feature, and mensuring again i percept the center of mass is another, and the z position is distorced. look in image 02


In the case of the assembly, the mass center in Z positions, is distorced in 150mm (it's too much). look in image 03

That error is and a dangerous information, because afects the project confiability.

And this case, i don't trust in that tool!

Can anybody here, explain to me, what are going on???

In my case, i'm using solidworks 2009 SP4.1 Premium in windows vista 64.

Thanks at yet

awainting some answers


Claudio