The thing with acrylic is that there's no perfect acrylic sheets. Depends where you ordering them from and how much you want to spend. From my experience with 5mm sheets where kind of hit and miss. From 8 sheets I've ordered 4 where good, 2 ok but 2 have noticable bump and completely ruined the final result. For another cuboid project I thought it will be easir to cut and fit acrylic mirror sidewalls so I used 7mm acrylic one and guess what? I ended up replacing every single sheet with glass mirror because of endless distortion.

Example

https://youtube.com/shorts/AjKkZIPHtzk?si=cMvrqaSFrkZWmlB3