This is a low-level ground tripod. This print will require a 3/8-16 by 1 inch cap head screw and a matching threaded nut. I also suggest using supports for the filleted sides as they are generic fillets and will print a little poorly without support.
Bill of Materials
1 x 3/8-16 by 1" cap head screw for the gimbal head mount (inserted from the bottom)
1 x 3/8-16 nut to secure the cap head screw (from the top)