Since every "official" throw is really a set of dozens of different related techniques, I am very open to variations which work for particular sizes or body types. My main concerns in evaluating variations are "Is it efficient? and "Is it safe?" If the answer to both questions is yes, then go for it. Once a student has mastered the basics (usually at 3 or 2 kyu), I begin to teach many different grips for techniques based on the student's preferences. I also teach lots of variations for combo techniques based on the uke's reaction. Some are standard throws, but most are some sort of application based on the principals of a throw rather than the technical throw as one might demonstrate for a promotion or kata. I also teach no gi variations, and without a gi, the grips and direction of kuzushi can change quite radically. Other considerations are age (with the related speed and strength issues) and injuries, particularly shoulders and knees. For example, a person who has difficulty squatting deep enough to execute a proper hip throw might have to adjust by taking a wider stance and throwing uke around his hip rather than over it.