Seriously,
I am not sure, But i Have seen alot of Drops that have been really good bird dogs.
In the past i have worked for Professional Handlers/Trainers that have had some of the top dogs in the country. (i will not mention names)
They had Stud Dogs that Bred anything that was willing to pay the stud fee
I have seen Brittanys bred to Setters and the off spring win a Brittany All-Age Nat. Championship.
German Shorthairs bred to English Pointers (didn't keep up with em)
Irish Setters bred to English Setters and i know of one that is winning in Open Shooting Dog now.

I Guess I wanted see what it would produce, i have never seen one or heard of it, evenas a mistake.