I was having real trouble printing the original arms for the Mad Cat MKII (http://www.thingiverse.com/thing:44025) without failing. Three consecutive prints failed at exactly the same place; the print head was hitting the print during a non-print move (which there's a lot of due to all the support material). Also, trying to clean out the support material inside the "shield" was near impossible due to the tight spaces. So, I redesigned the arms to be printed as two parts; a "shaft" and the "shield". This also has the benefit of being able to print them in different colors. :) The shaft can be printed without support (but I used a brim); there is a little extra material under the slot that needs to be trimmed away. I had to do a little shaving on the flattened end (making it nice and smooth) to fit into the Mad Cat's body; which is fine, you want it to fit snug. The shield still needs support but it is much less than the original single part. Once printed the shield slides onto the shaft (from the flattened end, up to the tab, which fixes its position on the shaft, and prevents it from rotating. Note: I printed the original model at 3500%, so the size of these parts is based on that final print size of the original parts.Print the shafts with a brim (a cylinder on it side mathematically only contacts the print surface at a line); that will give enough surface contact to keep it attached to the print surface, and helps the first few layers at the slotted end. The shield needs to be printed with support, of course, since it has 90-degree overhangs.