I have three different styles of hay feeders, single cradle, double cradle, standard ring and a "Bextra" ring.
Of all of them the Bextra wastes the least hay but they each have their benefits and drawbacks.
Where ever I have calves I use the cradles since they can get the hay out right down to the end of the bale.
The Bextra has benefits but big bales don't fit in it real well and there is always a point at which you have to do something (move the feeder spear over the top to shift the bale, etc.) to allow access to the center of the bale. The round bale feeders do have more losses but over all few problems.
The cradles overall are probably the best all around feeders. The bales are up off of the ground. What does fall thru is generally not trampled and they will retrieve it when they get to the end.
As mentioned above, I think it is a good idea not to put out more hay until they finish whats there otherwise why work at the getting the last stuff if that guy with the tractor is bringing fresh?
In the round feeders I drop 5x6's in from top, on end, with my loader spear on top of whatever is left. The cradles are naturally horizontal.
Jim