trick to spotting a catch dog prospect

I have 2 cur pits also and i have a ambulldog/cur cross. They are a really good cross. Especially for Running catch dogs. Mine do the same thing, they range out far and I mainly use them for my strike dogs but they will also catch. I keep a old english and ambulldog mix on a leash because he's so squatty. If you get them with too much old english in them,they come out so short, they aren't very athletic. But, when they do get there, they are like a boat anchor. Also, they have a very short snout so its hard for them to bite bigger portions of the hog. I.E. the throat and back of neck. But when they grab a leg or snout, its over, somethings getting broke. I use my little bulldog for insurance. If i have a big boy in the brush giving my dogs some problems, i send that little mobster in and he just starts breaking legs.