Apache + mod_rails apache config

We have a 2GB memory xen setup with ubuntu, apache and mod_rails only
(no db, etc.) -- is this a reasonable setup (taken from our apache2.conf

MaxKeepAliveRequests 390

StartServers 50
MinSpareServers 50
MaxSpareServers 50
MaxClients 400
MaxRequestsPerChild 0

What's the best way to optimize a server. We currently have 837 MB free
ram with the above setup, so I'm debating add more Start/Min/Max