I've been using the original for a while with good success, but I've always been concerned about the lack of having a 3mm nut on the second screw holding the brass piece, so I did a super simple adjustment to the model and cut out a section for one.

Printrbot

Printrbot Simple Metal

No

Yes

0.2mm

98%

Printed in ABS; 3 walls, bottom and top layers. Printed at a higher than normal temp to hopefully encourage interlayer adhesion.rnrnNote: I haven't tried this out yet so I may change the model later if I find it necessary.