You can also duplicate rows in C0, and then add columns, so you can get things like ⎛⎜⎝w0w1w2w0w1w3w2w3w0⎞⎟⎠. There are infinitely many biextensional Cartesian frames over {w0,w1,w2,w3} with morphism to C0, with arbitrarily large dimensions.
You can also duplicate rows in C0, and then add columns, so you can get things like ⎛⎜⎝w0w1w2w0w1w3w2w3w0⎞⎟⎠. There are infinitely many biextensional Cartesian frames over {w0,w1,w2,w3} with morphism to C0, with arbitrarily large dimensions.