I have been working on a assembly that is going to be symmetric about a plane....So I build one half of it and then mirror all the parts that need to go on the other side.......

As most of you may know that there is a need for a "opposite hand version" of some if not all of the parts.  In this assembly all the parts are flat plate...and I am using the mirror to keep from having to double the time to copy and mate all the parts again. 

After playing with the mirror function one of the plates was going to need the opposite hand version to show up properly.  Instead of letting the program make another part...I decided to leave this one part out of the mirror and add another part and just mate it up to where it will fit up properly.

What do most of you do when you mirror something and the program shows that you need a opposite hand version? Do you just go with it or see if you can really use the existing part?