I used to build all sorts of kits when I was kid. My father, brother and I all used to work on them together. I made one that was 3 feet tall, but only about 1/2"-1" in diameter. I lost it! it went about 2-3 times higher than I expected it to and I lost in the clouds (low clouds that day) and I never saw where it came down
They can be a lot of fun. But they ARE little bombs waiting to go off if you're careless. Take precautions and stay safe. I would suggest not using PVC
... at least if this is your first attempt anyway.