Hi Pasquale,
i plan to do use about the same configuration with the addition of using tux to serve static images on all of the web-servers. I have not started to look at lvs, but i know that the server-cluster thing in openacs deals only with the problem of server side caches that have to be flushed. Every webserver can notify the others when caches have to be timed out.
I will probably start in a few weeks to experiment and would be happy to hear about others experciences as well.
ciao,