This is a very powerful grip to use, it is also very tricky. Once you establish the Ippon seoi nage grip, you will have two options, you can either go for a real Ippon seoi nage, or you can switch to Osoto otoshi.
The beauty of this combination is that each throw has a different direction, Ippon seoi nage goes forward, while Osoto otoshi goes backward.
You can fake one of the two throws, then once you feel your opponent resisting it, apply the other throw and go in the opposite direction.