Rigid Materials (PLA, ABS):
Your current thickness of 6mm is appropriate for rigid materials.
Semi-Flexible (PETG):
Consider increasing by 1-2mm (recommended: 7-8mm)
Flexible (TPU):
Consider increasing by 2-4mm (recommended: 8-10mm)
Draw a smooth curve from left to right. This defines your rib's top edge shape.
● Your drawn line ● Smoothed preview (blue)