On my last sim check (B737) I got a low speed RTO (severe damage) circa 60kts! Very interesting! It's a sort of no man's land. Too slow for the rudder to be effective and too fast for the tiller. Differential braking seems to be the most effective in this situation. Using the tiller at this speed with asymmetric thrust just results in the nose wheel scrubbing along the runway. Worth thinking about!