Mammoth Pit Bulls

speed to me is a big big part of what i breed for...i let my catch dogs go from diff ranges but i find a lot of runners and if the cd isnt there in that few min bayed we wont stop it again..i would like to know how these big ones do also? i have one thats about 65..no where near 100 but with muscle some would say hes 90 ha i dont want any bigger than him because of thick brush...not because he gets stuck but because since hes so big he just busts thru it and tears himself up on briars and stuff..jmo though lol