You’d have to rebuild your site to use Foundry 3.
Yes, I know, which is why I am biding my time before biting that particular bullet! Anyways I have deleted the banner tool as you suggested and that, PLUS setting the cinema desktop height to 1300, seems to have done the trick. (If set to fluid it is still letterboxes as before.) If you have any further suggestions I am happy to experiment further, but thanks all the same for getting me to this point, which is a usable workaround as far as I am concerned.