There is an article written called "Buzzing Bees or Mushrooms" or something like that. It describes the aspects & pitfalls of CAS steel targets. That is the best piece of target lit I've seen. I recollect it was Sundown Jones who wrote it.
Calamity Jane (the Canadian one)
has a good synopsis(?) on the targets & stands with recommendations. It is good material she put together. It is on her website.
If you can't get it searched, email me & I'll can attach one or both to the reply.
Mustang Gregg
(target designer)