Hi OG,
I. Used a paper tube. My father ran a paper tube company, so I still have bits and pieces left. It was a four inch diiameter tube that just slid down in. The fur on the interior hid it.
A little more clarification. I only used the tube for display (which sadly was what it was made for). It was to hang next to a mounted buck that had been taken during archery season. I have heard the arrow rests across the antlers. I designed it with a double thickness of leather on bottom, so the quiver could be used. Their was enough of a lip of the fur, stitched in the upper interior to hold a properly cut length of tube in place. It gives the quiver a bit of stiffness and depth. I have a medieval one I made for a friend to use, the veg-tan leather is stiff enough to hold the shape.