I couldn't print the other stuff because it is grouped, but I thought I would try the test print.
Printed on Prusa MK3, Prusa Edition Slic3r, Optimal 0.15 layer height, 20% infil. It took about 8 hours to print the 3 test parts.
The Extension Leg part came out beautifully, but it was pretty tight. In the first picture, you can see it doesn't quite screw in all the way. If I put some force behind it, I was able to get it to fit squarely in the Upper Leg.
Once the Extension Leg is connected to the Upper Leg, there is still a small gap between them. Maybe enough to fit a piece of paper. But it's really tight. I have two guesses as to why:
1) The notch holes on the Upper Leg may not be quite deep enough. There was probably a little bit of sagging when printing the "bottom" of the holes, as they were facing downward on the print bed. Basically, the "bottom" sagged, and made the hole more shallow.
2) Similarly, screw hole in the Upper Leg, when bridging to fill the "bottom", the material sagged slightly, which doesn't let the Extension Leg fit perfectly into it.
Other than that, it printed pretty well.