I think it depends on how they were created. I NORMALLY get the option of "show dimension" when I right-click on the workplane in the browser. Then just change the dimension and update and the plane moves.
It's better if you can create the plane from one of the origin planes since these never change due to model changes.
For some reason, I'm not getting the 'show dimension' option. I have found that the dimension shows like a constraint in the selection tree and it is available for editing. Just wondering if this is an anomoly.
