@Ruda and @speedwobble thank you for your interest. I am afraid I currently have a buyer who is due to collect this weekend and even made a promise to a second person failing that, so it is effectively sold. I will close the ad when I receive payment. In the meantime, just for your information and in case the sale falls through:
The stack seems to be 27cm and reach 36cm, if I have measured correctly.
Unfortunately, selling eTap alone is not an option as this bike is designed to work with eTap and I don't have any other drive train to replace it with anyway.