Pic: would this chassis shape be legal?

[Creator Mat]

OK my team wants to do something like this (see attached pic) for our chassis shape. we follow the bumper rules. Would this type of shape be legal when herding the balls? I think it is legal because the ball would be free to move within the indentation area and thus would not be possession. I want to find out what the rest of the FIRST community thinks. Also if you think this would break a bumper rule or some other rule beyond just the no possession rule please say something.

Note: the red strip on the ledge thing on the top is supposed to be the bumpers