You can imagine all this by holding a stick as long as yourself, grabbing it from different locations and then rotating. Imagine there is a camera on different locations, and what it would look like from them.
Something you will notice, is that if you grab it from near the front and start turning it, the tail will hit other objects and your room walls more uncontrollably :p Actual ship turning speed is unaffected by where the core is, but if your ship core is at front of a very long ship, don\'t be surprised if turning suddenly stops as the ships back hits a station.
Also for docking purposes aswell the core should always be at the center of the ship.