var grid = Ext.define('MyApp.view.metadata.ResultGrid' ,{
    extend      : 'Ext.grid.Panel',
    alias       : 'widget.resultgrid',
    id          : 'mygrid',
    //columns, etc.

{ xtype: 'resultgrid', width: '85%', hidden: true}

var store = Ext.create('Ext.data.Store', {
    storeId     : 'resultsetstore',
    model       : model,
    buffered    : true,
    pageSize    : itemsPerPage, //50
    autoLoad    : true,
    leadingBufferZone  : 100,
    remoteSort         : true,
    //etc.

Ext.getCmp('mygrid').reconfigure(store);
Ext.getCmp('mygrid').show();

var grid = Ext.create('Ext.grid.Panel', {
    title       : 'Test Data',
    loadMask    : true,
    store       : store,

var grid = Ext.create('Ext.grid.Panel', {
    title       : 'Test Data',
    loadMask    : true,
    //...
});

grid.reconfigure(store)

var app = Ext.getCmp('my_container');
app.add({
    xtype: 'resultgrid', width: '85%', region: 'center', height: 400, collapsible: false, store: store
});