Sexing meat birds early?

[mcdaid36]

I posted something similar to this in the "What gender is this" forum, but thought some of you who have raised meat chickens before might know the answer. I have a batch in the brooder now - all came from same hatchery, hatched the same day, and are now 10 days old. They are Cornish Roasters. 3 have short stubby wings and no tail feathers yet, 8 have long wing and tail feathering. Is there any way to say that the 3 short stubby winged ones are roosters and the rest hens? See photos below.

 

[scooter147]

For what ever reason I can't see the picture but the easiest way to tell is by comb size on the birds. The roosters will have a largeer comb then the hens.
With meat birds it generally doesn't matter just butcher when they reach the size you want.
I always butcher a few at around 4-5 weeks as cornish game hens and butcher the rest 8-10 at a time as they get to the size I want, generally 6-7 pounds live weight.