Mirroring part in assemblies

Hello;

I would like to ask for advice on mirrored parts in assemblies.  I've experienced little success and it seems silly to rebuild a separate right and left part to get over the problem.

In this assembly, I have a plane which is angled to the left and mirrored it expecting to get a plane mirrored to the right.  Unfortunately the mirror inserted wrong and it has the same constraints as the origional part, preventing me from rotating it.  When I removed all of the constraints, the mirrored part rotated equal to the origional ensuring that at least one of them will be wrong.

I thank you in advance for any advice to resolve this or any links to help me with mirrored assembly components.

SolidworksAssemblies