to the best of my knowledge, there is not a way.
what comes after group footer or do you waste 2/3 of a page? what if the details take more than 1/3 of the page?
you can try making the group really big and having it always print at the bottom of the page, but if there are other items to print, I am not sure how this will work.
Maybe someone else knows a solution, but as far as I know, you're right and Crystal will print it relative to the details section.