I haven't seen complaints about cooling the 3 cf, at least on this forum. The n or st climate class for the smaller fridge means it works better in hot weather. Some of us on the forum have done a lot of research and some have tinkered with the enclosure, doors, venting, fans, you name it. Not to mention ETI has also been diligently working a solution with Dometic directly.
You can't make a subnormal fridge into a normal or subtropical, but perhaps they can get close with additional fans, box insulation or other 'fixes'.
One of my goals for my upcoming visit to ETI is to pin down the fridge model that will be used on mine, and verify it is NOT an SN rated fridge. I won't have one installed.
"You can't buy happiness, but you can buy an RV. And that is pretty close."