But the higher orbit would reduce the drag. You could probably get away with the same size sail, but you’ve got to start high enough that the sail’s tiny thrus

But the higher orbit would reduce the drag. You could probably get away with the same size sail, but you’ve got to start high enough that the sail’s tiny thrust over its 50% (ish) duty cycle can overcome the drag present in 100% of the orbit. Once you’re high enough a bigger sail would mean lifting the orbit faster.