Putter,
The log home builders cut a notch in the bottom of the logs with a chainsaw and slide the logs over a piece of steel, then drill a hole through the side of the logs and the steel so they can bolt them down. My concern with just sliding the posts over the pipe is that they will move on you. A strong wind will lift a porch off of a building, and fold an eave off the side of a house. Will you have a big parachute that wont make it though a severe wind?
I thought about using sono tubes, but got the idea to build the wood frames because of my plan to use brick pavers. I thought that it would look nicer to have the straight lines. Having done it this way, I now think that a sono tube would have been better and will use them on my next gazebo.
I'm really liking my C Channel approach. Each one is five feet long with five sacks of concrete in each hole. They are solid and easy to work with. I even like the look of the bolts, but then that's probably just me.
Your fire pit sounds intersting. I want garden furniture in mine and imagine it as an outdoor room to sit around, maybe have a meal with friends and just admire from a distance. I'm really curious how you do the ceiling and deal with the smoke.
I think it would be great fun, and probably educational to see what you do with your gazebo build. Feel free to post it on here with mine if you like.
Eddie