Update position mirrored assembly

[RichardFEMAP]

I have mirrored an assembly in Inventor 2010. I selected one of the planes of the original assembly as a mirror plane. The mirrored assembly therefore connected to the original assembly correctly.
So far, so good. Now I noticed that the width of the original asembly (in the direction of the mirror plane) was incorrect. After changing the width of the original assembly, the width of the mirrored assembly also adjusts (correctly), but there is now a space equal to twice the change of the width of the original assembly between both assemblies (incorrect). As the mirror plane was created on an end plane of the assembly where the mirrored assembly should connect, I would have expected that the position of the mirrored assembly would shift for both to meet again.
I cannot find the plane that was used to mirror back in my list of items. Where is this and/or how can I correct this? Many thanks in advance.

 

[arbreen]

While the mirror tool in a part creates a constraint, mirror in an assembly just creates new parts and does not constrain them. So, after you have used the mirror tool to create the new parts, you will still have to go in and manually constrain the L and R parts to each other. I'm guessing that the center point distance of the L and R assemblies is staying the same, and that you just don't have any assembly constraint.