I prefer thinner for a plains style quiver, so that when you bend over, the quiver is soft enough to push against your body and help hold the arrows in. That being said, 2.75 oz is quite thin. I believe 1 oz is equivalent to about 1/64 of an inch, so that leather would only be just over 1 /32" thick. It would probably work ok, but might not be very durable in the long run.
If I was you, I'd use around 4 oz. Even 6 oz is probably ok to use. Some people like to use thicker leather so that the mouth of the quiver stays open when putting arrows back in. But that also means the mouth is wide open when you bend over.
