That's an interesting speculation regarding the stern. Also they are not at environmentally sustainable since they require cutting down a very large tree of fine hardwood then only last about four years. A local guide used one as a mold and commissioned one to be made in fiberglas. It is the only one of it's kind in the region and will last pretty much forever since it can be easily patched.
Peter,
You must read about the international, (admittedly mostly French), fabulous self-help
boat building program in Bangladesh: "Whatever".
This program deals with the sustainability problem in Bangladesh of the desperately poor coastal villagers who man the worlds largest merchant fishing fleet of essentially large canoes. These boats use local wood which fall to pieces after 3-7 years in the water drowning the fishermen! The organization has introduced fiberglass with local jute fibers substituting for the more expensive Western industrial fiberglass. The charity Waterver, has also built an infrastructure of training, harvesting and preparing jute fiber, exports and boat building. now the boats can last 20 years or more.
Nicolas Claris and his son Romain have documented the entire program and I have one of the pictures used to raise money for the charity in my front hall!
Asher