noah,
i didnt feel like reading all of the post but in response to the topic, i say breed that dogo to one of your curs. the hardest cur you got. and i think you would have to keep the entire litter, you might only get a few pups that make it, which i think would be worth it, and as far as creating the "line" if you keep all your pups on all your breedings and cull hard, you will set the traits you want, but i imagine your cull rate will vary with every litter. it would be worth it even if you only get two pups out of the first breeding and culled the rest.
do you want to breed the dogo to your curs, or another line?
I've always known I could breed my curs to a catch dog and get better catch dogs... size is the issue however, as I've seen in horses... a draft horse crossed with a smaller horse always seems to produce larger progeny when the larger animal is the female... What I'm after is a larger version of what I already have, my Shiner dog would be the one I would breed, no doubt... but, I will wait for now... find a suitable "big female", that, once proven satisfactorily, I'll cross on a male from my stuff or something similar...