If the internals of the evap are not good which I suspect with that vapochill one it does not matter what your hx exit temps are because if there is not enough surface area to actually transfer the heat into the refrigerant and cause it to experience a phase change then it will stay as a liquid and evaporate in the suction line. On my cap in cap ebap I can have the ebap at -10c but the suction line at -50c