When I pick fish from fry I don't necessarily go for the largest, because I'm going to feed it the best food and keep the water up. That alone will put size on him anyway. I first look for the one with the best black line. Then if it looks healthy and well that's the one I go with. Idk but I've always ended up with very nice looking fish. Just my humble opinion.
A little update.... The male I kept from the batch of fry I had is not about 7" body length 8.5" in total. He's been sharing with Festae and now Istlanum and I think its about time I moved him into his own tank.