The banana plug expands into the hole so it won't fall out. So far it's the best removable pin I could find. It keeps the P1 from sliding off the platform. I cut a slot in the plastic to expose the vents in the bottom of the P1. I pressed 5mm (0.1969 inches) shelf pins into 3/16" (0.1875) holes on each side of the platform. These keep the P1 from spinning about the banana plug.
The tripod itself is an inexpensive one I found at my local Target store. You could use any tripod that has a 1/4" threaded post and doesn't interfere with the protruding banana plug. I found the approximate center of mass below the P1, then drilled (#7 drill bit) and tapped (1/4-20) the hole for the tripod post.
An easy project if you've got some tools. I cut the plastic on my bandsaw, then filed the edges smooth. I drilled a 5/16" hole for the vent slot, then used the bandsaw to extend that hole to the edge of the plastic. I used a drill press to drill all the holes. I don't recommend using a hand-held drill. I even used the drill press to press the metal pins into their slightly undersized holes in the plastic.
Those side pins were precisely positioned, and leave no room for the P1 to move between them. Notice that they don't block any vents or interfere with controls/jacks on the P1.
All in all I'm happy with this prototype. I like the clear plastic but it's gotten a little scratched up in the process. I've got some black fusion paint I may eventually use to paint it black. Stay tuned for my "Easy, Portable Projection Screen" post.