I filled the north poles with spray foam (Great Stuff Big Gap Filler) and let them cure for 2 days.
The north poles fell over because the foam pushed out the bottom...which is what I wanted. Today, I used a saw and sander to make the bottoms nice and smooth.
Here's how I cut the notches for the cords at the bottom of each pole.
Lastly, here's the video of the conduit being glued to the inside of the north poles.