I'm 6'3 weighing ~150 pounds, and one of my classmates is ~5'7 weighing ~210 pounds. Whenever I do rendori with him he always overpowers me due to his size advantage and low center of gravity. My sensei mentioned foot sweeps possibly being effective, but with his low center of gravity, I'm finding that to be just as difficult as a standard shoulder throw such as seoi nage Tips for what might be effective against him would be much appreciated.