Well, courtesy of the generosity of IanF, I finally got my hands on some polybeads.
..decided it was time to put my ideas for the ‘ultimate rear bean bag’ into action (having never understood why a tube seems to be the most common design).
The ultimate design…or so I thought (I’d unfilled it by the time I thought to take some photos):
I’d decided something triangular (a 3, 4, 5 triangle) would give me the most versatility….being easily changeable between the three heights. …..so made a 6/8/10” bag as shown…
Bottom line up front is that the design doesn’t work well! Poor ergonomics in its most stable position (the aspect photo’d) and not sufficiently stable in other positions ….back to the drawing board.
…..I suspect a 6” x 8” x 3” brick will be the next shape…unless someone has a better idea!