When training on running lines w/ 3 bumpers placed in series 6.5 month choc. lab female sometimes overruns 2nd bumper to get to 3rd. Shes definitely seeing it but just seems to be moving so fast she doesn,t stop. On way back she,ll slow down approaching that 2nd bumper and I,ll give her hold command and recall whistle and she continues in w/ bumper she was carrying. I thought spaceing bumpers about 30 yds. apart might stop issue but doesn,t seem to be doing it. My question is should I stop this before it develops into a problem that I can,t presently forsee.When she returns w that 3rd bumper I ,ve been sending her after 2nd bumper w no problem She never overruns first bumper to get to second and I,m trying to extend out her casts w this drill.