[chewy027]

There is no actual button to produce symmetry like in DOGA, but if you select the two objects that you wish to center at the same time (shift+click on both) then you can use the edit tab and use the align commands to center them. You can do this for as many Groups of objects as you want. So for example say you want to get your two wings as close to symmetric as possible in reference to the body of the ship. Eyeball as best you can and then select the wings and the body and align them either by the x, y or z axis.

note: To make centering objects easier try to do all your rotations with the camera angle and not the actual object itself. When you rotate the object itself it can skew the x, y and z axis and it will be much harder to align things properly.