<p>I want to provide silverlight app to my customer while hosting the app at my own site for streamlined maintenance.</p>

<ul>
<li>my Silverlight .xap  is hosted in, let say,  domain <em>me-supplier.com</em></li>
<li>i want to embed it in, let say, domain <em>my-customer.com</em></li>
</ul>

<p>It works perfectly for <em><a href="http://my-customer.com" rel="nofollow noreferrer">http://my-customer.com</a></em>, not for <strong><em>https</strong>://my-customer.com</em>  </p>

<ul>
<li>i have added the (<em>me-supplier.com</em> hosted) cross domain silverlight policy file to allow <em>my-customer.com</em></li>
<li>i have configured the mime types for .xap</li>
<li>the silverlight app needs html dom access so the iframe approach is not viable i believe.</li>
</ul>

<p>this works for javascript code, so why not for silverlight ? any idea, workaround ?</p>

The short story is that it isn't
easily
accomplished. That code is added to the header by the menu during the prerender phase.
A possible workaround might be overriding the menu's onprerender in a custom menu control and don't call base. You could then replace the default menu control with your own using
tagMappings
.
I'd suggest you stay clear of the menu control if you can.