Farmers'Walk Question

I’m putting on a multi-event contest that will include a farmers’ walk, and I’m facinated how the big boys are now handling 400+ lbs in each hand. Anyone have any idea as how far the World Class Elite FW beasts (Zavickas, Felix, et al) would be able to take 200 pound (each) implements for a ride in 60 seconds, with no put down? How about 225 lbs each?? Any world records established for implements of those weights?