My only fear would be the "cur" attributes coming out at exactly the wrong time.
Full catch or not, cur dogs just aren't bred with the same grit that bulldogs are. Interesting challenge you guys have taken on. Especially due to the fact that what your looking for would by most accounts be considered straight culls.
Also interesting is the fact that someone earlier in the discussion would consider straight-up generations old cow bred dogs to be these kind of dogs. Every single person I know of that works cows would be handing out dirt naps to dogs that continuously caught out. To me, a cow-bred dog should be one of finess and working style...a get ahead and bunch them type dog. Surely not one that uses his mouth very often.
Good luck, and I look forward to hearing about your progress. Just as a sidenote, I keep American Bulldogs (although they're not yellow...and have no black mask) for all the reasons you don't keep pits.
When I read the 1st post this is what came to mind. Just to expand on this, guys with Abs you have to know how they are bred. With them it matters. That's why so many people have been disappointed. You cannot just get anything from anywhere.