What I'm more into with the use of Latex for casting is using it for one-shots and things. For me, sometimes you need a cheap but good cast of something you'll use once and basically discard (more or less). Latex is useful/cheaper for that mode of thinking generally while RTV Silicone's going to be a little more complex and costly overall...
BTW the technique Glassman picture-by-pictured there is a great one to use Paul, that's a very useful one for hollow helmets I think... I hadn't really looked back through the thread before my reply so I was speaking from my own personal methods, but his picture tutorial was quite easy to follow.