When a mate and myself build a pulk we used the Osprey Bio Form.
I insisted in having a quick release system given that there was the possibility of the pulk (or him) falling through the ice.
No shoulder harness was used.
Max weight pulled about 40kg
You can see it in this shot.
The "pulk" there is just for training, in Alaska a modified Paris sled was used .
Note PVC tubes and climing ropes were used, no metal bits.
(for field maintenance)
The connecting point is where the Iliac crest is.
We tried different spots that worket best.