In the upcoming 4.0(5) release you will be able to configure the Custom Keymap conversation (one of 6 or so conversations you can select from) to have a key that skips the message header and goes right to the body - which is what you want.
In the current 4.x line there is no key map for this available - but you can make it do what you want by setting the "Conversation - Do not replay message summary" value in the Advanced Settings Tool to "1" - then when the message header plays (this is also call the "summary") you can hit "*" to skip to the end of the message and then "1" to restart the message - this will restart the message at the begining of the message itself when you have that advanced settings value turned on. So you'd hit "*1" and the effect would be you skip the header and go right to the message.
A little awkward, but it does work.
