jsGrid Dynamically change the inserting property value

Thanks for this great software.

My question is, How can I remove/hide the insert icon (+) when a certain number of lines has been reached. I have to validate how many grid lines are when the page is loaded so if is <=4, insertions is allowed otherwise the + icon must be hid, also if I have three lines and inserting the fourth, after saved it the + icon must be hidden.

This what I have and is not working, url validates and return true/false

var allowInserting = xyz //value when the page is loaded
$("#jsMyGrid").jsGrid({
    inserting: allowInserting,
    ...
    controller:{
        insertItem: function(item){
           type: "POST",
           url: "url",
           data: item,
           success: function(data){
                     this.inserting = data.data.message;
                     $("#jsMyGrid").jsGrid("refresh");
                    }
        }
     });