IIRC the drivers including all their kit and their seat have to be a minimum of 80kg, and they try to be as close to it as poss to avoid being disadvantaged. If they're under they have ballast added to the car, they used to be able to choose where it went but now it gets added to their seat unit.
The taller guys still seem to really struggle with it. Bottas has mentioned that when the weight limit went up it allowed him to gain half a stone and it allowed him to be in his comfortable athletic weight range rather than obsessing and calorie counting.
When Di Resta was commentating an FP1 last season he was saying that he's so tall he really struggled and had to ration himself on race weeks, to the point that he didn't have tea on Friday nights bless him.
Off to Silverstone this week, checked the weather and it's looks like a scorcher. Currently preg so that's gonna be fun