Unfortunately, there isn't a sure fire way. The best that i can suggest is counting / measuring where you are on the page and then forcing a 'New Page Before' if the measure is over a certain amount.
Create a formula for each section of the report. All that this formula does is increment a shared variable by the height of the section. In Section Expert, for the group header in question, in the New Page Before section add a formula that references the shared variable and returns true if the height is over a certain amount. In the page header section, reset the variable to the height of the section.
It will get you in the ball park, can't guarantee anything, Crystal can be persnickedy at times. Sections with a field that Can Grow will also mess with this calculation as you may not 'know' the height of a section.