I also use 8-9 oz on holsters for the most part. They are easy toi wet mold and retain the shape unless you over-oil them. And, like Rube mentioned, do occasionally have used thinner leather like 7-8 oz for smaller pistols.
I did make a pair from two layers of 8-9 oz leather one time. They were a bear to wet mold but when done, you could drive a truck over them and not hurt them.
When we get enough response to this thread, I'll add it to our FAQ list for easy location in the future.