Boss design is a common design in a plastic part, it is used for mating part or for attaching fasteners such as screws or accepting threaded inserts. if our engineers design a bad boss in a plastic part, we will meet many molding problems, so I think The wall thicknesses of a boss should be less than 60 % of nominal wall. of course, it depends on the boss’ position in a plastic part, if it is in an unimportant or invisible position, the wall thickness can be increased a little. even can be used self-tapping screw, a greater radius at the base would be better, a least 0.25 x thickness. Gussets or connecting ribs reinforce the boss.