Since GTM doesn't support document.write() method the standard clicktale code doesn't work. Is there a workaround for this?

ClickTale employee has sent me these instructions:

Replace the document.write JS line above with the following: 
document.body.appendChild(externalScript);

Example:
<!-- ClickTale Bottom part --> 
<script type='text/javascript'> 
var externalScript = document.createElement('script');
var scrSrc = document.location.protocol=='https:'?
'https://clicktalecdn.sslcs.cdngc.net/':
'http://cdn.clicktale.net/';

scrSrc += 'www11/ptc/xxx-xxx-xxx-xxx.js';

externalScript.src = scrSrc;
externalScript.type = 'text/javascript';
document.body.appendChild(externalScript);
</script> 
<!-- ClickTale end of Bottom part -->

I am not sure what to do with this. Has someone tried something like this?