I have a friend who has a Rottweiler & it is a Big dog. She walks it everyday.
I made a dog collar for her, out of a single layer of 10-12oz veg-tan.
Over a years time, that collar stretched a bunch. Like way worse than I thought it would. IDK maybe it was a bad side of leather I got or what.
I made a new collar for her, out of 2 layers of 8-9oz veg-tan & put velodon no stretch fabric in between the 2 layers & sewn it with 346 thread.
It has not stretched any in over a year now.