InstaDMG customizations?

Hi all, Sorry if this is redundant, but I've searched the boards and couldn't find a clear answer (watch someone link). I'm wondering how to create an InstaDMG image but remove the welcome/registration screens and, once turned on, immediately display a login screen. I've got pretty much everything else down: creating users, applying updates, etc. I'm just stuck on this one area. Any suggestions? Thanks so much!