I know of 2, 25" collie Grey x bull Grey's that did them on regular occations before the ban ,also a sapling that has.
Heart has more to do with it than size,
Saw a 28+ deerhound cross pull up on roe,
So I figure the size isn't a guarentee.
As to the the original question whether the bloke could own 3 that do it single handed,well he is a lucky man,especially if the can potentially catch 100 rabbits too.