Females can grow closer to 3 inch (just had a quick peek in the downstairs tank to check this).
They are hardy but do need the substrate to be kept clean, especially in hot weather, as they are prone to bacterial infections. I am doing twice-weekly gravel vacs on my tank as I lost one cory in the hot weather.
Also, sand is best, but if they're on gravel it really needs to be smooth gravel so their barbels don't wear down, as they need them to find food.