Thank you that dose work. But what about the main assembly planes. If I have a very large mod (say 50' x 120') up and I need to find the center plane it can be so small I canot use it. A part might not be sitting directly on the plane I need.
I can't seem to find a way to resize the assembly origin planes either. May I ask why this would be important? If you are trying to constrain to them you can always select them in the model tree. I know that isn't the answer you wanted but it may be a good work around. Sorry I can't be of more help.
At first you need to change the selection method in the assembly environment to Feature priority instead of component priority. Then you can resize the assembly origin planes.