Acrylic is generally a pretty brittle material that cracks and breaks with ease. We were quite surprised at how effective this pattern was for bending it.
3mm acrylic is possible, but 2mm really shines. We can go a full 180 degrees, but over that you hit the "Ummm... is it going to crack?" threshold. We're trying experiments with varying cut depth, as full cut-through is most flexible, but we have one sample with a "kiss cut" through the backside that practically seals when you bend it. Looks promising. Will publish more data later as experiments progress!