How big do these guys really get and what is the best way to sex them at 4''?
As far as I know, they are Vieja. As for sexing, I have yet to find out a significant way of sexing any of the Vieja. I have all of the Vieja's and they are about 6", and I cant find any differences that will lead me to make a good determination.
Thats what I would say. I dont think that I have ever seen an Argentea, Blackbelt, Synsphilus, Regani, over 12".