Is there a proper way of setting SortOrder on a new entity when saving it in Umbraco 7.1.8?

Default the SortOrder is set to the highest number +1 when a new entity is saved, but I want it to have the lowest -1, so that the entity will be the first in the list.

I have tried to set it on the events Created and Saving, but it seems to be overwritten when Saved.

I have solved it for now with the code below, but I wonder if there is a better way/best practice to do it?

        void ContentService_Saved(IContentService sender, Umbraco.Core.Events.SaveEventArgs e)
        {
            var contentTypes = new List() { "Nyhet", "Rundskriv", "Sirkulaere" };
            if (e.SavedEntities.Count() == 1)
            {
                var entity = e.SavedEntities.First();
                if (entity.IsNewEntity() && contentTypes.Contains(entity.ContentType.Alias))
                {
                    var parentEntity = entity.Parent();
                    if (parentEntity != null)
                    {
                        entity.SortOrder = parentEntity.Children().OrderBy(n => n.SortOrder).First().SortOrder - 1;
                        if (entity.Published)
                        {
                            sender.SaveAndPublishWithStatus(entity, 0, false);
                        }
                        else
                        {
                            sender.Save(entity, 0, false);
                        }
                    }
                }
            }
        }