The arch is probably the most classic design for the mac stand.

For a mac stand, I only have 3 requirements: usable, simple and looks nice(very personal). This design fits them all.

This stand is for MBP 13' retina. the dimension of the upper most part of the opening on the top is 18mm. A scaling may make the stand fit for other models of mbp, I didn't try it.

The mac_stand_v2 is with an opening whose upper opening dimension is 18mm and the lower opening dimension is 15mm, this design provides a firm grip of your mbp.

The mac_stand_v3_not_so_tight version is with an opening whose upper opening and lower opening dimensions are always 18mm, and the mbp can be put into and pull out easily.