I spun up a new planter holder. Hopefully it will work well, I'm a little worried it's too weak. It might be solved by shortening the cup on top and rounding the points...
Eh, I'll see in 4 hours
It seems ok. I should have made it about .1" wider (2.5 mm) but it stretches enough. The bottom angle could be better but given the error in diameter it's shallower angle works better.
I am starting to think i should make my own inspection tools or something to measure angles and stuff instead of just guessing or holding an object in front of my screen (that trick worked better when i could see closer)