I'd leave the tarp rectangular. Not that cutting cat cuts is difficult, but I think you'll find more pitching options with the square sides. Add a few more tie outs and then you can more easily pull in the sides to make doors, pitch it on the diagonal during calmer weather, and have more of an awning for "porch mode." I think jacks r better have some good photos showing off their rectangle tarps in such configs.
The cat cuts are helpful to eliminate loose, flapping material, but you can get pretty close with good pitching. It won't be 100%, but close.