I'm working on a model in a top layer assembly and including one simple sheet metal part only, I'm trying to mirror componenet that has a mirror derived config inner (do not want  add 1 more seperate mirror part)  but it doesn't work. Solidworks gives the following error: "This function has not been implemented for models with multiple sheetmetal base features (some of wich may be hidden)". Does anybody know how to solve this and does somebody know why Solidworks can't fix this problem? because this happened several times. 

I've included the model in the attachement

Thanks in advance!