The one in the last picture? Yeah, the ventrals are too long for a girl, I think.
I actually do have some girls with crazy long ventrals but I agree, along with the beard it's a good sign of a boy. Another easy way to tell is to look for the ovipositor (egg spot) on females. Of course, juvenile males can sometimes have them too so it's not foolproof
I recently added three of my juvenile girls to my sorority tank... and when I finally saw them all together, I realized that my second smallest "girl" was a tiny boy all this time XD I've had the fish since they were 6 weeks old and all this time, I thought he was a girl and named him Stella haha!