Don't know about your simmentals, but my idea of "big framed, carrying good flesh", is definitely different from yours.Check out the specs of For-most's 30 head gate. http://www.for-most.com/model30.html 27" at the widest. I've seen several cows and quite a few mature bulls that absolutely can NOT walk through it, no chance in he!!. The only way to get them out of the chute is to let them out the side gate.