I ran the solver from 250k to 375k. Still no solution. To cover my tracks, I also did a 1x1x1 cube. It was solved almost immediately. Tomorrow I’ll try another test box. I’m assuming a 3x4x2 would give a good solution.
Also, why can’t people have real numbers on the load bearing capabilities of 3/4 pvc? I’ll probably make my plant wall with it anyway, but it would be nice to know how much weight it could take. I think I’ll get my pieces, and then start putting fixed lengths under load and measuring the deflection.