Some rabbonim are wearing really long and large talith katan. For example Rav Shmuel Auerbach shlita (picture below).
Rav Elyashiv ztl used to wear a very long one too.
Which shita are they following?
This is quite a bit longer than Chazon Ish shiur; I wonder if perhaps it has something to do with the Gra, as I read that he requires the talith katan to go down to the knees. (See note 10 here.)