[R]Replace request content using Request Filter Groovy scrip

Hi,

I'm trying the replace the request content using a RequestFilter.filterRequest using SoapUI Pro 4.5.1

I do request.setRequestContent("New message content")

However for some reason it doesn't it doesn't take effect until after the request has completed. I would have thought that filterRequest should be able to change the outgoing content before it is sent.

Is it possible to do this?

Thanks,

Joel