Works great for an iPhone 6 with a slim case. Printed this from the OctoArm-v3-Old-Tighter.stl file.
3D Solutech PLA
(For anyone with the MPMD, I used the "MPMD Fast" profile from the mpmd wiki in Cura 3.6. I'd planned to turn off the supports since I read that they're not needed on this, but forgot.)