Also, you should be able to copy the sub element like so (I currently use this to copy sub elements from a cell that has not been plotted yet) :
Element newElement;
using (ElementCopyContext copyContext = new ElementCopyContext(Ms.GetActiveModel()))
{
copyContext.WriteElements = false;
copyContext.DisableAnnotationScaling = true;
newElement = copyContext.DoCopy(elementToCopy);
}
return newElement;