hi there,
You are correct, you will need to connect the hard disc recorder via scart in order to distribute the picture to another B&o tv, as the RF modulator needs a composite video signal to work. In addition to masterlink you will also need to combine the rf aerial output of the beovision 7 40 with your aerial system, as the picture is distributed via aerial. B&o make a specific product called the RF LINK amplifier, or you can use stock combiners if you are au-fait with aerial systems. The key thing to bare in mind is that unlike older products the rf does not loop through the tv, the output from the bv 7 40 is only the distribution frequency, and not the normal tv channels as well.
Also if you have sky and are using the RF2 output of that to power link ir recievers in other rooms you will have to be careful not to ground the power sent out of the sky box.
Is your dealer fitting the set? If they know your system, then they should be prepared for this upon installation, but it might be worth talking it through with their installer.
Hope this is useful
Mark