You can ditch all of the spacers, but it is better to have one for ease of adjustment. I've ridden bikes without a washer with no problems for years. In fact I think my beater has no spacer. Additionally, you don't need to have all of the threads on the locking ring. It will be OK as long as you get a couple on there. Still, it could be tight-are you sure the seller is measuring things the same way you are?