We chose to use legs with adjustable height to ensure a perfect even air table. If the air table is not even, the platform drifts to one side and by this induces a bias of the mouse to one side. Additionally to that one can counter biases of mice by making the platform uneven. Some mice tend to prefer e.g. the left lane.
To each optical post add a 90 degree angle{Qty:4}.
To achieve the verticality, put in each 90 degree angle an optical post (length: 100mm){Qty: 4}.