My first rail was scaffold pole approx 5 m long. wedged between two upright RSJs that formed two uprights to a shed. Two spare timber baulks kept the pole about 3 m off the ground, with a couple of chocks driven in at either end to keep it steady. S hooks held the deer on the rail. It took a bit of manhandling to slide big reds along the pole. The original hoist was a stationary chain hoist.
My point is that we never had issues with 3 or 4 big reds on the pole. Perhaps there is a difference between steel scaffolding poles of 30 years ago and whatever material is in use today.