Postby prkos » Sat Mar 14, 2009 11:21 pm
Although it's been requested before it's not possible to change the coordinate system, maybe in one of the future versions.
But you can achieve what you want very easily using the Align dialogue, Grids or Guides, and even easier with the new snapping options that are available in the development builds.
With the Align dialogue you can center objects to page, or to one another. You can use grids with the geometric option for objects bounding box so you can set the dimensions without rounding errors and snap them to grid.
The easiest way is to use development build with snapping toolbar. There are options to snap to object centers and rotation centers, midpoints of bounding boxes which seem to be what you need, and lots of other useful features... You can install the dev build independently of the official 0.46 version so you have both at the same time, it's worth a try.
There was a Mirror Live path effect but I think it's not available atm, but you probably only need Clones. Create one object (or group of objects), make a clone and move it to it's position, flip it if necessary. This way when you edit the original clones will update automatically.