IE 11 Compatibility Mode

I have a site that uses an older version of Infragistics controls, in particular the UltraWebGrid. That grid does not display correctly in IE 11 unless I add the site to the Compatibility List. I've tried adding the meta tag

<meta http-equiv="x-ua-compatible" content="IE=7" />

using various values in the IE=? . When using F12 tools I can see that the document mode is getting set to what I expect but the only thing that results in the page displaying correctly is to add my site to the compatibility list. I can also change the user agent to IE 10 or lower via developer tools and that also makes the site display correctly.

I've contacted Infragistics and they aren't any help.

I do plan to upgrade to a new version of the Infragistics grid but it will take several weeks until I can complete that so I would like to do something in the mean time to make my site work again.

Is there anything I can do that will have the same result as adding the site to the compatibility list? Or any other suggestions?

Thanks