Master metrics - leading problem

While designing diacritics on uppercases, I faced some problems concerning the leading. I set the metrics to sum up 1000 units (from 800 to -200).
When I test it in text the diacritics and descenders come dangerously close. Should I change the metrics to adjust the diacritics or should I make the uppercase smaller? Why is it important for the metric to sum up to 1000 units? (see photo bellow)

thank you,

The metrics don’t need to sum up. I see it as a recommendation. Did you read this:

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