Here is the way I fixed mine incase of high winds.
Here you can see the end of the PVC I cut at an angel to help when driving it into the ground.
Here you can see the stack driven into the ground through the base.
Here you can see the main stack centered in the base of the obelisk.
This is the second piece of the foam (blocks from a cheep fogger box) It is tightly wedged in to the end of the obelisk, for the stack to fit into to help stabilize the upper part in case there was to be winds.
Here is the second foam piece of the inside of the obelisk, it's a larger foam packing from something I or a friend got (LOL). With a hole for the stack to run through; it helps to stabilize the upper part of the obelisk, closer to the base.
Obelisk without Gargoyle lights
Enjoy