I believe you could use RequestEvents.Prepare to let Kentico know that the current request is SSL using:
RequestEvents.Prepare.Execute += PrepareExecute;
and
private void PrepareExecute(object sender, EventArgs e)
{
if ((HttpContext.Current != null) && (HttpContext.Current.Request != null))
{
// check current domain
var domain = RequestContext.CurrentDomain;
if (domain.Equals("yourdomain", StringComparison.OrdinalIgnoreCase))
{
// use SSL for english versions
RequestContext.IsSSL = true;
}
}
}
And then you can simply enable SLL on your IIS for the domain you need :-)
Additionally you could Redirect (301) user in this event if the current protocol is HTTP and not HTTPS. I personally avoid redirection if not necessary and think that IIS would handle this better. Still, its definitely an option..