Wow! That is a bright lemon yellow your son chose! (
Maybe so they can see it in the dark at night?
)
I think I would have wanted to tone it down a bit, too.
I've never used the rubber washers or Velcro on any of my cages, do let us know how well it works for you.
I even considered placing on the back side where the chins can't reach it ...
That would be a very good idea ... if they can get behind it, they can make it move.
Jo Ann