I printed the smallest one but am having issues with the legs connecting to the hips. The joint between the two is really loose and doesn't seem to quite fit properly. The problem seems to stem from the fact that the front and back of the hip balls are flat which definitely doesn't fit in well with the rounded inside of the leg joint. If the hip ball was rounded it would fit perfect similar to how the feet fit with the legs (rounded part fits into the rounded recessed spots inside the joint instead of flat).
I am going to try and reprint the legs with a slightly different orientation to see if they got warped a little bit during the original print but I don't think it is going to matter.
Overall, I really like the design, just wish the ball parts weren't flat in some spots that contact the inside of the joints.
Lulzbot Mini ABS .18mm, 20% infill
Edit: I printed one of the other models you made with the partially rounded joints and it worked perfectly. For reference I did you Killer Kommando V1.3 http://www.thingiverse.com/thing:554283