CaptainBerz posted a three part video of how to make your own inexpensive tripod hog style saddle.
The first video is just Berz and Nate talking about the benefits of shooting with a tripod and saddle. They did mention that shooters would use PVC pipe and cut it in half. While this is better than nothing, it is not as stable.
Video 2 delves into the components and how to assemble the shooting saddle. It uses a galvanized framing bracket.
Stay tuned for the third part as it is not up yet. I suspect it will cover how to pad the framing bracket and possbily how your rifle will interact with this shooting tripod.