Update: I designed three more clips and added them to this Thing. The new ones were done in DesignSpark Mechanical so I was able to round edges.
I redesigned the board clip, shifting it off center, and using the stronger gripping profile from thing:219651.
Printer with ABS, 0.25mm first layer, 0.2mm remaining layers, no support, 30% infill. With all long, thin printed parts like these, using a brim will help keep the part from curling off the print bed.