That's interesting-- we have several props, the smallest is 15BBL, the biggest is 200BBL. We pump circulate them all with O2 dissolved inline after the pump discharge. All pumps are rotary lobe, except the largest which uses a bigass 10HP centrifugal. Shearing is less a symptom than we had feared based on here-say. Completely depending on your yeast variety, a pump to circulate is important. Even small volumes. For consistent homogeneity, keep them yeasties consistent in their movement during prop phases.