The key when doing beaver tails is cutting the back side (where the stitching is) just slightly longer than necessary so it puckers slightly.
I use a hole punch now and have for years with much more success than the chisel hole. Just know that you can't pull too hard on the stitching or you are going to rip the tail. Leave it a little long as mentioned above, and you will no longer need to pull so hard.
I have brown and black tails in stock.
BigJim