If these boxes are going to be cast in concrete as in a cell pour I am not sure how you would get them to move at all. There are enough irregularities in a regular box that would give a pretty good bite. I had an octagon that was cast in place and one ear had a rusted in place screw. I took the ring off the connector in back expecting that a few taps with a hammer would dislodge the box. I ended up having to use a piece of #3 rebar like a drift punch and beat the snot out of the inside of the box, all around to get the concrete to release it's grip. YMMV depending on the slump and how much they vibrate the pour. They usually pour cells here at a 5 or even 6. That is a McDonalds milk shake. There will probably be a little grout in the box through the small holes
