We have our welder in the shop drill a hole through the side at the top where the puck fits in and the welds a nut on the outside. We then use a thumb-screw to go through the hole and hold the puck in place.
This is an older one before I figured out the right pipe ID so they made something out of what they had. Too bad the thumb-screw assembly is on the other side. Just dig a 1ft hole and fill it back it. They have proven very stable for the life of the project.
