Beyond the usual “good form” of throwing your training partner in keeping your back straight and knees bent seoi nage can and should be practiced in two ways. The first is how most of us learn the waza (technique) where you take hold of your training partner, turn your back, and throw them over your body. This works very well, but when applied against a training partner much bigger (bulk) and taller then you often the throw becomes less practical as bad habits like bending your back start to happen in order to heft the other persons weight over. When this happens modifying the technique (henka) becomes important- taking your training partner and their weight over your hip almost slinging them around if you can’t switch to another throw. Of course knowing which throws to match up with the correct situations is important, and in the dojo easy, but in actual application it doesn’t always work out that way.