The inside foot placement is traditional and is the way everyone teaches it. Whereas most people try to learn UM (a difficult throw from) day one, I didn't really learn it (or really practice it much) until I was a brown belt. It never worked. It all clicked for me during a clinic where the visiting sensei suggested the outside foot placement. That placement, coupled with the natural pull of the left arm across the body, made the throw really work for me. As you see in the video, my pull is quite violent, which pulls him off balance as his hip comes into position, making the rotation even faster.
At this point I can do it either way (inside or inside) with no problem (I scored ippon with an inside foot placement in my last tourney). But it was this different approach to it that enlightened me to role of foot placement, hip placement, and locking-hand pulling.
The grip I use in the gi is similar to way you do yours without a gi. You can also use a whizzer grip or, my personal favorite, around the the head. I've seen a lot of no-gi UMs take a deep initial step (with the eventual reaping leg) to place the hip, rendering the placement of the plant leg a little less relevant. It might be difficult to do it the way I demonstrated in no-gi unless you had a really good grip on the other guy's wrist.
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