They recomend 3 to 4 wraps under the reins with a normal size heel knot. Example I have one particular smaller 5/8" bosal with a heel knot that is larger and heavier than normal.  With that bosal two or three wraps would be about the same as three or four wraps with a normal bosal. But nobody is saying that 2 wraps wont work on a standard bosal. What they are saying is that 3 or 4 wraps will work a little better. It will give you a better release because of the weight. But your rope weight and your heel knot size plays all into this.

All this little stuff adds up in the end. Example in hair ropes there is about a 1/4 pound difference between an 8 strand and a 6 strand rope and a 6 strand and a 4 strand rope has another 1/4 pound difference in it. The diameter of the rope makes a difference to. Example a 4 strand 3/4" rope and an 8 strand 5/8" rope weighs about the same.

Example you can start a colt in just one 5/8" bosal, not make any rope changes.Then when you have him trained, put him in a 3/8" two rein and you can make a nice horse.

But the guys who are turning out the best hackamore horses, who have their horses working inside the hackamore. They are useing several different bosals in each size and making rope changes as the horse is ready for it.

With myself I only own one bosal in 3/4", 5/8",1/2" and 3/8". But I use vet wrap on them when the time comes in each size for the horse to use a softer bosal. I also change my ropes. But im also planning on buying more bosals as finances allow because the more steps you can put into this process the easier it is and the better the end result will be.