You really need to get rid of the boards/cardboard. It traps heat and can cause the chicks to overheat and promotes pasty butt. Use a piece of window screen and binder clips to secure to the totes.
Having it off to one side is good. They need a cool side to get away from the heat and that is...
Please post pictures of your setup.
It would be highly unusual for them not to go under the heat source.
I assume you have secured the top with screening of some kind to prevent them flying out?