There will no doubt be an E89 member answering soon, but after looking at one on the BMW stand over at the FoS last Friday, the boot looks a little larger with the roof up. That of course is completely destroyed when down although I guess it would be fine if you were carrying shallow objects.
- E89 is 180 litres with roof open and stored and 300 litres with the roof closed.
- E85 is 240 litres with the roof up yet reduced to just 220 litres with it down.