you're not understanding basic laws of scienceSingle digit body fat is incredibly hard to get to. I don't think you understand that. Keeping it there requires giving 100% effort year round, which is harder than you're making it sound.
you do not gain weight unless you eat above maintenance level calories. This rule does not change at 9% BF or 20%. Are you saying its difficult to eat 2500 to 2800 calories?
getting down to 9% is very hard, maintaining is pretty easy