Bosve,
Up by 2mm!? That's not what you said originally. Originally you said down by 1cm. So has it changed?
If you have the Row Spacing set to 0, and the height of the labels is 7.5cm, and there's no margin between the physical labels, then the height of the Detail section of the report should be 7.5cm.
Unfortunately I can't really give it a good test, as with the file you sent I get a whole string of partameter prompts and error messages about mussing files and whatnot, which I don't really have time to try and track down and correct for. But if you keep fiddling with the settings in the report design, and note what difference they make, it will help you sort it out eventually.