Change some image properties fields of 'Image' control

Hi!

I need to change some fields for 'image properties' tab (default HSpace|VSpace to 8px and change width to 750px when image with width more than 750px is uploaded).

What i've tried:

CKEDITOR.on('dialogDefinition', function (ev) {
    var dialogName = ev.data.name;
    var dialogDefinition = ev.data.definition;
  
    if (dialogName == 'image') {
        var infoTab = dialogDefinition.getContents('info');
        var hspace = infoTab.get('txtHSpace');
        var vspace = infoTab.get('txtVSpace');
        hspace['default'] = vspace['default'] = '8px';
       
    }
});

But when image is uploaded hspace and vspace sets back to 2px.

Also, i think it's possible to write onChange handler to txtWidth and change input value properly, but i think you can write more suitable for me.

Thanks!