I’m one of the stoker stem users.
I bought a few before finding one that worked, which was non-adjustable amd was the lowest angle stem I could find, paired with the longest quill stem, a piece of handlebar, and two bar-ends. It was heavy, and wouldn’t adjust very far forward. Here’s a thread with pics.
I’ve since purchased a Nimbus Shadow, broken it, and now I have a new one. It is NOT as adjustable as the KH, but there are some really sweet things about the design. The best is the improved seat rigidity from the way the seat-base attaches. The seat is rigid at the front. but seems more comfy due to the fact that the middle of the seat is NOT right on top of the post, but rather slung between the front and back, sort of like a taint-hammock.