I'm installing a vinyl replacement patio door. The rough opening is complete and I've assembled the frame. However, I haven't been able to get a straight answer as to the proper method of installing the frame in the opening. There are no predrilled holes in the jambs or the sill, no shim spacing requirements and no vinyl covers in the channels to hide mounting screws. Does anyone know how many screws should be used, and their proper location? The instructions do not include this information.