didi, The double-walled example above has been been smoked, daily, going on two+ months now.
bright, LOL. Guess I've been smoking "grass" legally, then. :0)
Thanks for the link. Very interesting. Learning more about this wonderful, natural resource. I was concerned that at least the node wall, which is the bottom of the bowl and get's burned, would quickly burn through as it's softer material. Not so. Care must be taken when scraping. I use a bamboo shard to clean it out, then I remove the filter from the stem, point the pipe over the trash can and blow forcefully through the stem to clear the holes in the bottom. Two months of this and no issues.
I also plug the bottom chamber with a disk of willow, a soft, non-toxic wood. I tap it in there with a finishing hammer, the bamboo will stretch to accommodate and creates an airtight fit. This can easily be removed by running a wire, from a coat hanger, through one of the holes at the bottom of the burn chamber, for cleaning.
All my gun springs are still in use. You can buy generic springs in bunches at the local hardware store.