They wont DQ you for long legs but your bird wont place as well next to a more stout d'Uccle.
Here's an example of a show quality d'Uccle. We wont even look at its color, since yours is a white and this is a mille fleur, but it has pretty nice type:
This birds tail should come out of its back in a bit more of a V than a U, but it does has a nice, erect, full tail at a good angle. Also see how his legs are shorter than yours? Yours also doesnt have much of a neck, it's more like his head just runs into his body. (it's still a beautiful pet quality bird, im not trying to be mean, but critiquing always sounds harsher than its meant xD sorry )
I also found a picture of a show quality WHITE d'uccle rooster to better help you understand!
The rooster isn't really posing, unfortunately, but you can see how nice and full his tail is, and how it comes out of his back in more of the desired V than the U in the previous example. This birds legs are a bit long too, but not too bad. I can also tell he has a nice full neck, even though he's in an angle that shows it the least.
So I hope that helped you get a feel for the standards of perfection of d'Uccles. I really want to encourage you to go to a show, even if that means bringing this rooster with you, so that you can see other birds and get a better feel for type.
