Our load balancer works at a lower level of the OSI stack, and it can therefore not perform this.
I've found that it is the application com.sap.engine.docs.examples which binds the / context root, and I can always (re)move this and create a new J2EE application which does the work. But this is uneccassary complex.
The HTTP alias, are as the name implies, and alias, and not a redirect.
How has other portals solved this problem?