I'd move the shift button further from the 1p joystick the way it is you could be hitting it while you're moving and creating all sorts of gameplay nuisances. If you don't have more room than the dimensions you've laid out, then I'd personally put the shift button in the top middle of the control panel. That way it would balance out the layout, wouldn't get in the way, and both players could have access to it (assuming it's needed for certain player 2 controls).