So Michael,
Are you going to model the “Double Bow-Knot” in your garden?
It has been years since I read the book you mention but if memory serves there were two or three Shay’s that had the sloped oil bunker like your # eight shows. I think these were used mostly in reverse service to the Summit of the mountain so the fuel oil had somewhere to go besides all over the outside of the bunkers.
Great stuff.
Rick