Eutetic in one compartment it is always difficult not to freeze the milk.
The hassle is the plate must be at least 5f deg below the fluids freezing temp to solidly freeze the plate. A lower temp will freeze the plate a bit quicker.
Our solution was an Igloo to hold the stuff we didn't want frozen , while freezing the plate with the engine drive..
WE had 2 sections, a 0F freezer and a 28F fridge , but the 28F plate was in series with the 0F plate so would go to -10f while cooling.
In port only the 28F plate was cooled by a small 120v compressor , which worked for a weekend.
Some folks have used a folded "space blanket" to create 2 sections.