Is there a way to have cisco smart install delete the current config on the client switch before proceeding with the update of an ios and new config?

I have cisco smart install working great. The client switches I am updating were used in another environment and still have their old configs. I have noticed that if I try to do 3-4 switches at a time, some of them wont go through for one reason or another, and just stop before the ios even begins to upload over tftp. If I go and delete the config files from flash and do a reload, it works fine. So this tells me that something in the old config is stopping it from working. Is there something I can configure on the director switch that will delete the config files from the flash before the process of uploading the new ios and new config begins?