There are many crab droid variations out there, so let me start off by saying that the one I have built is the six legged ones from the battle of Utapau, Ep.3 Revenge of the Sith :) It was pretty challenging coming up with a movie accurate design for the legs, whilst keeping it small. It is still a little larger than minifigure scale, but it is close enough, and I believe making it smaller would mean sacrificing key details and components.
I'm super stoked with how it came out in the end, and i'm happy to finally have one of these bad boys on display :)
Quoting Jp ...
Great take on this droid, would have loved to see more pics of it. You really nailed a lot of subtle details with a very limited amount of pieces. The face is especially well crafted ! Bravo :)