Hot air rises so the higher the clip the "hotter" the air it's exposed to.
And thus the COLDER the fridge
Addition of fans to the INSIDE (And outside) of the fridge can improve performance as well.. I have two "Computer type" fans (12 volt fans) in the outside compartment blowing UP. there are multiple designes for these fans and multiple locations you can put 'em (bottom or top of stack) these improve cooling.
and I have two more inside circulating air.. They help too.
There is a light/fan "kit" that mounts at the top of the fidge that is about 100 bucks from I think CW and other suppliers that I plan to add once I get the Fridge working..again.