Questions about space stations?

Refer to: <a href="/node/4722">Space Stations: Rotation Speeds &amp; Size Specifications</a>.<br /><br />any way to know what a space stations width will be on the wheel?<br /><br />Does the a space stations wheel need to be a circular tube? Could it be a hexagonal tube or a square tube?<br /><br />Would ships docking to the outer wheel unbalance a station's rotation?