I like the idea of it being a counterweight etc birdlady. I'm just not sure about hanging the bags up for the simple reason that even if Ken climbed on that table, i don't think he could reach high enough to hang the bags up. Why have them so far out of reach if they're just counterweights? More likely, whatever they do, brings the bag down to them.

I do think that the painted boards on either side of them look to be a measuring line. Once whatever they have to do reaches the top of the painted section, they win.

The yellow bag does look lower than the red one. It could be the angle though when comparing Corinne's height to Susie's height in other pictures, it looks relatively comparable to this photo, which would lend a little creedence to your thought that the yellow bag may be lower than the red one. But then when you look at the table height, it comes up to Ken's waist while it looks to come up only to Bob's knees. I know Ken is shorter but..... lololol

i almost see a rope coming out of the top of Susie's head but i can't find a comparable one over on Kota's side so i'm discounting it for now.

I do think you're on the money with the counterweight thingy. :)