I have sat in a few tri-pod stands over the years that I just haven't been comfortable in due them being generally small where the seat/covered area is and they seem to move to much. I would recommend the enclosed black plastic barrel looking stands that you put up on 4 - 4x4 posts and have a door and several drop down windows. We also have a stand that we built from the ground up in an opening like you are describing (no trees around) and it came out very sturdy and can sit 3 people, but it was a lot of effort. Especially building it away from your home garage full of tools and power supply.