At first blush, I would say that those look like calf headlocks, that have been widened out........ As if they should be taller for that size animal.  

I'd agree that the pivot point may be low as things are and raising them may solve your problem if they are sticking their heads in and not getting locked but the dimensions you mention seem about right.  ......If they won't put their head through to eat, that is another deal.