Consistent Java versions

Hi,

I've a need to support some older firmware out on some industrial PCs. Some of these don't work so well with all versions of Java and we end up having to have seperate PCs each with its own version installed. Sometimes though these get updated by mistake and its a bit of a mess, so I wanted to see if portableapps could help. I suspect this is something thats already been achieved here but I can't find anything in a search of the forums.

My idea was to create 3 installations of portableapps. All with firefox portable, but each with a separate version of jportable: 1.6, 1.7 and 1.8

So I've completed this, and when I browse to the industrial PC and open a console, it prompts me to use the Jportable launcher, but for each installation its always running Java 6 (which is the version native on this admin PC). I had expected it to run the version of java local to that installation.

Have I missed something basic ?

Thanks for the help.