Although not a Centruroides species, Babycurus gigas gets pretty large, but I don't know if they go into 7+ instar, or if they get the same length as C. bicolor. C. bicolor is the longest bark scorpion I've heard of. I'm not so sure about other Centruroides species. I bet once you compile a list of the largest Centruroides, everyone is gonna want to buy them. People just love huge scorpions, haha.