I've found several posts talking about this issue, but none of them seems to be fully applicable to this specific case.

I'm fetching data from a jsonp feed (similarly to what is done by the "Getting Started with Sencha Touch 2" guide).

This works fine, but both Ext.plugin.ListPaging and Ext.plugin.PullRefresh plugins duplicates data when activated.

As far as I've understood this is caused by the missing idProperty, but frankly I don't know how and where to set it from a feed.
This feed doesn't have any ID, unless you would consider the title an ID and even in this case, I don't have a model where to set this ID, as the feed is not controlled by me.

Here's the config section of my view:
    config: {
        title: 'News',
        iconCls: 'star',

        items: {
            xtype: 'list',

            plugins: [
                    xclass: 'Ext.plugin.ListPaging', autoPaging: true
                    xclass: 'Ext.plugin.PullRefresh',
                    pullRefreshText: 'Pull down for more news!',
                    releaseRefreshText: 'Release to refresh...'

            emptyText: '<p class="no-searches">No news found</p>',

            itemTpl: Ext.create('Ext.XTemplate',
                '<div class="news-item">',
                '<span class="posted">{[this.posted(values.publishedDate)]}</span>',
                    posted: timeAgoInWords

            title: 'Latest News',

            store: {
                autoLoad: true,
                fields: ['title', 'author', 'content', 'contentSnippet', 'publishedDate'],

                proxy: {
                    type: 'jsonp',
                    url: 'https://ajax.googleapis.com/ajax/services/feed/load?v=1.0&q=http://www.beneventocalcio.it/index.php?format=feed&num=20',
                    reader: {
                        type: 'json',
                        rootProperty: 'responseData.feed.entries'